Game crashes gives you error and closes the game when exiting cave if you stay longer. After reloading game you apear near the sinkhole like nothing happened and can continue play.
Another bug with ruins: after genereating ruins you can see your character going down the rope and game just freezes forcing you to exit. As far I tested it happens only first time you enter!
Enter caves, play for a little and try exiting caves - error gona show up. Enter ruins for the first time it gona freeze your game! Both are simple as that!