Hey there pandafox, I'm having a wonderful time playing The Master Key. I'm on Level 7 with the shifting walls stuff, and I managed to get myself stuck. If you don't do things in the proper order, you''ll get into a fail state in this dungeon.
IIRC, once you beat the third Ogre, you're supposed to take the passage he comes from, then go north and east past the 'prison' room, then go south and back through the crab passage and end up back in the room with the pit. However, I then went past that room and back into the 'prison' room, and found that walls had sealed off the passage I mentioned earlier, and the way back to the room with the pit was also blocked. I could not get out. Fortunately I had a nearby save ready, so I wasn't bothered, but I think this is something that should be looked at. Combined with the 'Random Number Scavengator' on Level 2 and the crash on Level 6 with the '73 seconds in Hell' puzzle (I got it while a monster was attacking me), I'd say there is reason for a small update to this fantastic mod.
(I had a go at The Chaos Key, and I didn't like it as much. The pacing is all wrong and there are too many puzzles at the start.)
Keep up the good work!