When you add items to your empty offhand using 'f' (or just the assigned key in general) you duplicate the items.
When you place a single item in an item frame you get a 0-stack
Linked issues
is duplicated by 7
MC-93616
0 Items in stack crashes the game
Resolved
MC-93621
Item dupe
Resolved
MC-93638
i placed a map on a item frame and it gave me another of the same map except this one is gliched
Resolved
MC-93656
Switching Items into Offhand via Hotkey duplicates item
Resolved
MC-93671
items in off hand bugs
Resolved
2 more links
Attachments
Comments 5
I can also confirm this by posting a video of how to do this glitch.
(Note: This is for educational purposes only)
Likely related to MC-93592.