So, I just recently started working on stuff again and noticed that when I'm working on a map and I use the selection shortcut (Shift+CTRL+Left Click) on anything on the map to select it again quickly, the map freezes and only fixes upon closing and restarting DM. Oddly enough, you can still do things to the map (you can see it happen on the minimap area) but the main map screen is essentially frozen and goes completely blank if you switch to another tab and go back.

I was originally using 501 and it happened, so I switched to the most recent Beta build and it's still happening. Not sure if it's just me or not.