Not exactly a typical 'bug', per se, but it is certainly an unintended issue: after mining rocks within the entrance room of the Cave Cleft, the items that are dropped may occasionally settle behind the graphics for the Spooky Hole. Normally this isn't an issue, as you can just rotate the screen around, but in here, that's not an option. Now, although I was able to just barely click the pixel to pick up the item (a gold nugget, go figure) that was nearly completely hidden behind the graphic, it most certainly required an excessive amount of finesse.
Since I imagine this is not an intended feature of the game, I wanted to make sure it was indicated in the bug forum.
Steps to Reproduce
Mine in the Cave Cleft. Get unlucky with where the contents of your rock settle after being expelled from the boulder by your pickaxe.
This issue has not been confirmed by a developer yet.