I found two buried treasure maps in shipwrecks as well as traded/bought an Ocean Explorer map from a cartographer villager. All three maps are completely blank of any information or images. I reinstalled Minecraft and now the maps function as regular maps – they only display the area I'm in and have traversed, with no markers and all are identical as a result.

Attached are photos of the blank map, and of the map behaing as an empty map after reinstalling.

I also play on a survival multiplayer server and have been able to use the maps successfully to locate buried treasure there.