Field template settings not applied when using a custom view-mode (on paragraph items)

I have a paragraph field: content_blocks

then I have a couple of paragraph bundles ... the ouput is like I want on "expert" when I select view-mode "full" for the paragraph items
but when I switch the view-mode of the paragraph items to "content block" (a custom view mode) ... the template output returns to default drupal field output
(eventhough the field template settings are saved correct in the manage display page).