I found a hole in my world in the shape of a battle tower with all of the spawners just kinda floating in the hole. I got a fatal error message when I flew around in it. It didn't crash my client but it did screw up my save to where if I try and get back in it it gives the same fatal error, terminating connection or whatever.
Edit; It doesn't seem to only be the battletowers. I keep find areas where it looks like a square structure or something was supposed to have generated but either only the loot and spawners gened or the walls/structure glitched out and disapeared. If I go in to the area where there was sup;posed to be walls/etc it glitches out the world and gives a fatal error.