Steps to Reproduce

1. Put item frame on the ground
2. Use this command:

   /tp @e[type=item_frame,limit=1,sort=nearest] @s

3. It looks like the item frame is facing a weird direction, and you can use the following command to see the strange Rotation of the item frame:

   /data get entity @e[type=item_frame,limit=1,sort=nearest] Rotation

4. Re-logging will fix the item frame.

Orignial Description

By placing two item frames in the same blockspace, using a corner wall, and teleporting entities in that blockspace to another location, will result in an item frame that holds the other item frame at the new location .... this Item Frame is also indestructible, and blocks block placement.

1. I placed two item frames in the same blockspace, but putting one on one side of a corner block, and another on the other

(Warning! crude drawing ahead)
------ [block]
b---] [_____]
l ---] — x —
o---]-x
c---]
k
consider this as the corner placement, and the two x's as item frames attached to the walls of the corner.

2. I had an ArmorStand occupy the blockspace

3. I ran an /execute command to teleport all ItemFrames in the same blockspace as that ArmorStand, to another corner with another ArmorStand

4. the ItemFrames teleported but like so

---] [_____]
---] — x —
---]
---]

With the second item frame displaying inside the first item frame.

5. I broke the block that was supporting the item frame, it persisted.

6. I used a piston to push the blockspace, it persisted.

7. I attempted to place a block in the blockspace, this was not allowed as an entity was considered to be there.

8. I relogged to ensure it wasn't a graphical glitch, and repeated steps 5-7, the Item Frame persisted

9. I used the /kill command targeting ItemFrames, the ItemFrame was removed.