Map Graphical Glitch

Alright, noticed this a little while back on 1.1.5, thinking it'd be patched by 1.2, but, nobody reported it. So here I am!

Anyways, after re-logging into my Realm, I get this graphical glitch with my maps. It's mostly an annoying bug, because after replacing the map in it's frame, the lines disappear. Not sure why this happens, it just does.