The bug

Item frames in inventory lose their Invisible or Fixed entity data tag after upgrading.

To reproduce

1. Create a new 1.20.4 world.
2. Execute the following command:

   /give @s item_frame{EntityTag:{Invisible:1b,Fixed:1b}}
   

3. Place the item frame down.
4. Save and close the world.
5. Reopen the same world in the latest snapshot.
6. Place the item frame down.

Expected result

The item frame would still be invisible and fixed.

Observed result

The item frame is visible and not fixed.