Big graphical glitch

[Lightning4]

My friend found a hidden cave. Something was odd about it though. He entered and said that it had forest tiles inside, and wasn't loading the cave map properly. Walls weren't visible either.

Relogging (lolstuck on people) caused the cave to load properly... but leaving the cave causes this:



EDIT: Moving away from the cave enough causes the forest tiles to pop back to normal. Unfortunately, this also results in the cave tiles unloading again.

[Brosephine]

I had this too. At the same cave, I believe.