The Adam hotfix on 20 DEC 2022 resulted in weird green squares appearing all over custom maps, like this:

The solution is pretty easy. Go into your settings, click the "GRAPHICS" tab, then "ADVANCED GRAPHICS SETTINGS" and make sure "WORLD DECALS ENABLED" is disabled/unchecked:

And that should fix it. Note that the custom map "22nd Street" will still be broken even with this fix, but all other maps I've tested so far have been fine.