I have tested a few of my games on EasyRPG Player and while it's handy to have RPG Maker games portable, I've found it does produce its own share of bugs and errors. Not sure about the crash, maybe EasyRPG handles something out of order sometimes and trips up? The bugs it generates where otherwise there are none are always very strange. It also likes to make tiles face Up unexpectedly, which can cause things to look wrong.
The things in the STAIRCASES are indeed meant to disappear into the walls/out of your way, though.