On updating the world from 1.20.4 to 1.21 the maps (locked and unlocked) are losing their NBT data and becoming 'Unknown Map' when in glow item frames and will not display.

When picking item from frame it displays in hand as a blank map.

1.20.4 and 1.21 screenshots included to show issue.

This is a major problem for long term worlds where progress has been mapped (like my own).

Thanks!