File Field Values Not Saved on Form Submission when Child of Flexbox Layout

When adding a file field as a child of a "Flexbox Layout" item, the file is uploaded but the value is not saved on form submission; that is, there is no value in the "value" column of the "webform_submission_data" table.

Looking specifically at the logo_upload field on a real life form:

Does Not Save Value on Form Submission:

ppa_contact_info:
  '#type': markup
  '#markup': '<h3>Contact Information</h3>'
group_1:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  organization:
    '#type': textfield
    '#title': Organization
    '#title_display': before
    '#required': true
  website:
    '#type': textfield
    '#title': Website(s)
    '#title_display': before
    '#required': true
group_2:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  name:
    '#type': textfield
    '#title': Name
    '#title_display': before
    '#required': true
  title:
    '#type': textfield
    '#title': Title
    '#title_display': before
    '#required': true
email_phone:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  phone:
    '#type': tel
    '#title': Phone
    '#title_display': before
    '#required': true
  email:
    '#type': email
    '#title': Email
    '#title_display': before
    '#required': true
ppa_organization_info:
  '#type': markup
  '#markup': '<h3>Tier 1 Only</h3><br />'
tier1_group1:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  press_briefing_room:
    '#type': select
    '#title': 'Press Briefing Room'
    '#title_display': before
    '#options': yes_no
  shelving_preference:
    '#type': select
    '#title': 'Shelving Preference'
    '#title_display': before
    '#options':
      Slanted: Slanted
      Straight: Straight
  booth_id_sign_copy_organization_name_:
    '#type': textfield
    '#title': 'Booth ID Sign Copy (organization name)'
    '#title_display': before
top_five_booth_preferences_if_floor_plan_is_ready_:
  '#type': textarea
  '#title': 'Top Five Booth Preferences (if floor plan is ready)'
  '#title_display': before
tier_1_and_2:
  '#type': markup
  '#display_on': both
  '#markup': '<h3>Tier 1 and 2</h3><br />'
  tier1_2_group1:
    '#type': flexbox
    '#attributes':
      class:
        - 'form--inline clearfix'
      style: form-group
    logo_upload:
      '#type': image_file
      '#title': 'Logo Upload (high-resolution, .eps or .jpeg file)'
      '#title_display': before
      '#required': true
      '#file_extensions': 'eps jpg'
    print_quantity_for_distribution_of_show_materials_:
      '#type': number
      '#title': 'Print Quantity (for distribution of show materials)'
      '#title_display': before
      '#required': true
    print_date_when_materials_should_arrive_at_your_office_:
      '#type': date
      '#title': 'Print Date (when materials should arrive at your office)'
      '#title_display': before
      '#required': true
      '#format': month_day_year
print_material_address:
  '#type': address
  '#title': 'Print Material Address'
  '#title_display': before
  '#required': true
  '#address__required': true
  '#city__title': City
  '#city__required': true
  '#state_province__required': true
  '#postal_code__required': true
  '#country__required': true
quotes_for_use_by_pmmi_in_promotional_materials_press_releases_e:
  '#type': textarea
  '#title': 'Quotes for use by PMMI in promotional materials,  press releases, etc.'
  '#description': '<p>(please include an attribution name,&nbsp;title and organization name)</p>'
  '#title_display': before
  '#description_display': tooltip
specs_groupd:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  print_digital_ad_specifications:
    '#type': textfield
    '#title': 'Print/Digital Ad Specifications'
    '#title_display': before
    '#required': true
  ad_specs_upload_optional_:
    '#type': managed_file
    '#title': 'Ad Specs Upload (optional)'
    '#title_display': before
    '#file_extensions': 'gif jpg png pdf'
  print_digital_ad_deadline:
    '#type': date
    '#title': 'Print/Digital Ad Deadline'
    '#title_display': before
    '#required': true
    '#format': month_day_year
specs_group2:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  website_newsletter_ad_specifications:
    '#type': textfield
    '#title': 'Website/Newsletter Ad Specifications'
    '#title_display': before
    '#required': true
resources:
  '#type': markup
  '#markup': 'Please provide an actual (or estimate) reach number (subscribers, members, attendees, registrants, etc.) for each of the promotional resources available to your organization. Additionally, provide the relevant name and/or description for each.'
website_group:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  website_s_:
    '#type': textfield
    '#title': Website(s)
    '#title_display': before
  website_reach:
    '#type': number
    '#title': 'Website Reach'
    '#title_display': before
publication_group:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  publication_s_:
    '#type': textfield
    '#title': Publication(s)
    '#title_display': before
  publication_reach:
    '#type': number
    '#title': 'Publication Reach'
    '#title_display': before
newsletter_group:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  newsletter_s_:
    '#type': textfield
    '#title': Newsletter(s)
    '#title_display': before
  news_reach:
    '#type': number
    '#title': 'Newsletter Reach'
    '#title_display': before
email_group:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  email_list:
    '#type': textfield
    '#title': 'Email List'
    '#title_display': before
  email_list_reach:
    '#type': number
    '#title': 'Email List Reach'
    '#title_display': before
membership_group:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  membership:
    '#type': textfield
    '#title': Membership
    '#title_display': before
  membership_reach:
    '#type': number
    '#title': 'Membership Reach'
    '#title_display': before
social_media_group:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  social_media:
    '#type': textfield
    '#title': 'Social Media'
    '#title_display': before
  social_media_reach:
    '#type': number
    '#title': 'Social Media Reach'
    '#title_display': before
other_group:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  other:
    '#type': textfield
    '#title': Other
    '#title_display': before
  other_reach:
    '#type': number
    '#title': 'Other Reach'
    '#title_display': before

Saves Value on Form Submission:

ppa_contact_info:
  '#type': markup
  '#markup': '<h3>Contact Information</h3>'
group_1:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  organization:
    '#type': textfield
    '#title': Organization
    '#title_display': before
    '#required': true
  website:
    '#type': textfield
    '#title': Website(s)
    '#title_display': before
    '#required': true
group_2:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  name:
    '#type': textfield
    '#title': Name
    '#title_display': before
    '#required': true
  title:
    '#type': textfield
    '#title': Title
    '#title_display': before
    '#required': true
email_phone:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  phone:
    '#type': tel
    '#title': Phone
    '#title_display': before
    '#required': true
  email:
    '#type': email
    '#title': Email
    '#title_display': before
    '#required': true
ppa_organization_info:
  '#type': markup
  '#markup': '<h3>Tier 1 Only</h3><br />'
tier1_group1:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  press_briefing_room:
    '#type': select
    '#title': 'Press Briefing Room'
    '#title_display': before
    '#options': yes_no
  shelving_preference:
    '#type': select
    '#title': 'Shelving Preference'
    '#title_display': before
    '#options':
      Slanted: Slanted
      Straight: Straight
  booth_id_sign_copy_organization_name_:
    '#type': textfield
    '#title': 'Booth ID Sign Copy (organization name)'
    '#title_display': before
top_five_booth_preferences_if_floor_plan_is_ready_:
  '#type': textarea
  '#title': 'Top Five Booth Preferences (if floor plan is ready)'
  '#title_display': before
tier_1_and_2:
  '#type': markup
  '#display_on': both
  '#markup': '<h3>Tier 1 and 2</h3><br />'
  logo_upload:
    '#type': image_file
    '#title': 'Logo Upload (high-resolution, .eps or .jpeg file)'
    '#title_display': before
    '#required': true
    '#file_extensions': 'eps jpg'
  tier1_2_group1:
    '#type': flexbox
    '#attributes':
      class:
        - 'form--inline clearfix'
      style: form-group
    print_quantity_for_distribution_of_show_materials_:
      '#type': number
      '#title': 'Print Quantity (for distribution of show materials)'
      '#title_display': before
      '#required': true
    print_date_when_materials_should_arrive_at_your_office_:
      '#type': date
      '#title': 'Print Date (when materials should arrive at your office)'
      '#title_display': before
      '#required': true
      '#format': month_day_year
print_material_address:
  '#type': address
  '#title': 'Print Material Address'
  '#title_display': before
  '#required': true
  '#address__required': true
  '#city__title': City
  '#city__required': true
  '#state_province__required': true
  '#postal_code__required': true
  '#country__required': true
quotes_for_use_by_pmmi_in_promotional_materials_press_releases_e:
  '#type': textarea
  '#title': 'Quotes for use by PMMI in promotional materials,  press releases, etc.'
  '#description': '<p>(please include an attribution name,&nbsp;title and organization name)</p>'
  '#title_display': before
  '#description_display': tooltip
specs_groupd:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  print_digital_ad_specifications:
    '#type': textfield
    '#title': 'Print/Digital Ad Specifications'
    '#title_display': before
    '#required': true
  ad_specs_upload_optional_:
    '#type': managed_file
    '#title': 'Ad Specs Upload (optional)'
    '#title_display': before
    '#file_extensions': 'gif jpg png pdf'
  print_digital_ad_deadline:
    '#type': date
    '#title': 'Print/Digital Ad Deadline'
    '#title_display': before
    '#required': true
    '#format': month_day_year
specs_group2:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  website_newsletter_ad_specifications:
    '#type': textfield
    '#title': 'Website/Newsletter Ad Specifications'
    '#title_display': before
    '#required': true
resources:
  '#type': markup
  '#markup': 'Please provide an actual (or estimate) reach number (subscribers, members, attendees, registrants, etc.) for each of the promotional resources available to your organization. Additionally, provide the relevant name and/or description for each.'
website_group:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  website_s_:
    '#type': textfield
    '#title': Website(s)
    '#title_display': before
  website_reach:
    '#type': number
    '#title': 'Website Reach'
    '#title_display': before
publication_group:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  publication_s_:
    '#type': textfield
    '#title': Publication(s)
    '#title_display': before
  publication_reach:
    '#type': number
    '#title': 'Publication Reach'
    '#title_display': before
newsletter_group:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  newsletter_s_:
    '#type': textfield
    '#title': Newsletter(s)
    '#title_display': before
  news_reach:
    '#type': number
    '#title': 'Newsletter Reach'
    '#title_display': before
email_group:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  email_list:
    '#type': textfield
    '#title': 'Email List'
    '#title_display': before
  email_list_reach:
    '#type': number
    '#title': 'Email List Reach'
    '#title_display': before
membership_group:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  membership:
    '#type': textfield
    '#title': Membership
    '#title_display': before
  membership_reach:
    '#type': number
    '#title': 'Membership Reach'
    '#title_display': before
social_media_group:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  social_media:
    '#type': textfield
    '#title': 'Social Media'
    '#title_display': before
  social_media_reach:
    '#type': number
    '#title': 'Social Media Reach'
    '#title_display': before
other_group:
  '#type': flexbox
  '#attributes':
    class:
      - 'form--inline clearfix'
    style: form-group
  other:
    '#type': textfield
    '#title': Other
    '#title_display': before
  other_reach:
    '#type': number
    '#title': 'Other Reach'
    '#title_display': before