The resource pack attached offers a complete fix for this issue. Mojang have my full permission to (and are encouraged to) replace the affected vanilla model files with the contents of the resource pack.

Download resource pack:

• 21w41a: frame-fix-21w41a-v1.0.zip

The bug

The model for item frames which contain a map contain four faces which cannot be seen without clipping into the item frame. These faces, while visible on normal item frames, are completely obscured in the map item frame.

How to reproduce

1. Place an item frame on a fence
2. Place a filled map inside the item frame
3. Walk into the item frame such that your view can see the inside rim of the item frame, which is something never otherwise visible

Expected result

As these faces require clipping inside of the frame to see, there's no point in rendering them, and as such they would be omitted from the model.

Actual result

The faces are still there, despite not needing to be.

How to fix

The resource pack attached to this ticket removes these four faces from the map item frame, completely fixing this issue. As a bonus, it cleans up the formatting of not only the map item frame model file, but also the normal item frame model file, the four model files that point to these two template models, and the two blockstates files for item frames and glow item frames, to be more consistent with other models and improve readability. (The templates would certainly benefit from cullface arguments, however as item frames are entities, they cannot use cullface at all.)