Thank you for your post!
I am not seeing an issue seeing a PDF in a Container Field set for Interactive Content when "Insert PDF" is used.
-Can you confirm how the users are inserting the PDF files? (Insert File, Insert PDF, DragNDrop)
-Are the files Stored as Embedded into the file or using External Storage?
-Do you have the option to "Export Field Content" when seeing this issue?
-Have you been able to reproduce this behavior in a new file?
I look forward to your response!