Locked Maps on Realms show chunk errors when re-logging.  See attached image.

The map sometimes then partially re-loads the area onto the map with updates if any have been made.  This partially re-loaded map is then, still locked until the player re-logs.  Re-logging only seems to show the updated area not the original, locked map however.

This only occurs on Realms (tested locally on Windows 10) and occurs on both Windows 10 and Switch (both running 1.19.30)

It looks like this also affects un-locked maps which initially show chunk errors, and then load in correctly if in the area the map is showing.  This makes me think there is an error with the way the game is saving/re-loading maps.

EDIT: This seems to only happen when you are in close proximity to the map's location.  Moving far away and then re-logging doesn't seem to affect it.

This means maps are currently unusable on Realms.