I found this bug with maps in the snapshot that would show random markings that weren't in the world, and it's been around since 20w20a. I've checked in the other dimensions and it only seems to not happen in the nether, it happens in the end too.
[media]Related issues
Attachments
Comments
migrated
[media]
galaxy_2alex
Duplicate of MC-179858, please read the moderator note on that report.