I had one of my players reporting this weird map issue. Said it's happening to him on multiple computers.

He's saying it happens after he's been logged in for a while and that reconnecting fixes it. The map screen isn't frozen or anything while it happens.

He said this has been going on for a while but this is the first I've heard about it.

For reference, the map should look like this

Map with reported bug:
https://i.imgur.com/g4hG12z.png?1

What the map should look like:
https://i.imgur.com/6usofVs.png