I can't replicate it on demand, but something about tar is making the game unstable. The crashes most often occur when a mob first steps on it, but seeing as tar is most often combined with turrets, it could be any number of things; bullets hitting tar, mobs dying on tar, gold dropping on tar...
It's definitely something to do with tar. What, exactly, I have no idea.
It's definitely something to do with tar. What, exactly, I have no idea.