Media library checkboxes invisible

I'm using a gesso-based theme with Layout Builder. When I try to create or edit a custom block that uses an image from the media library, the checkboxes to select an image can't be seen.

Here's the markup:

<div class="views-field views-field-media-library-select-form js-click-to-select-checkbox"><span class="field-content">

<div class="form-item form-item--checkbox form-item--id-media-library-select-form-0 js-form-item js-form-type-checkbox js-form-item-media-library-select-form-0 has-no-label">
      
<label for="edit-media-library-select-form-0--94vaNsPW6fQ" class="form-item__label visually-hidden">
    Select Merlot jelly with brie and blackberry tarts
      </label>
        

<input data-drupal-selector="edit-media-library-select-form-0" type="checkbox" id="edit-media-library-select-form-0--94vaNsPW6fQ" name="media_library_select_form[0]" value="10" class="form-item__checkbox">

        </div>
</span></div>

I suspect the problem is that the label is before the checkbox, where the code in _form.item--checkbox.scss seems to expect the checkbox to come first. Instead of expecting a particular order, could the code rely on being a child of .form-item--checkbox instead?