I've played partway through the level, here's a condensed report:
Button does nothing? Advance along the corridor, read notes on walls. Order, direction, color?
Go left twice, find large empty room, keys begind gates.
Leave, go left, corridor with trapdoors. Open/close pattern too complex to figure out quickly, fell down. Two snails in small room, beat one, new one appears? Flee outside. Teleporter takes back to trapdoor corridor.
Get past the corridor (wait for quick close/open, move on next close), skeletons come from behind secret doors. On killing second one game crashes with message "mod_assets/scripts/monsters.lua:159: attempt to call global playsound (a nil value)". (playsound should have capital S?) Happens same way on repeat attempt.
Leave skeleton room, still go left, find branching corridor with teleports. Teleport maze. Eventually find new corridor, secret button on wall, get longsword.
"Beware the obvious!" Ordinary button trapped? Press secret button, gate opens, kill slime. Press wall button, another room opens. Point of message unclear. Something different happen if press buttons in different order?
Leave the room, find note. Hint for later puzzle?
Room with levers and button. Based on note, try up/down/down/up/up, door opens. Out of curiousity try different combination, struck with ice, door closes. Open again.
Skeleton archer, kite back to room and kill there.
Room with button, feels like trap, got to press anyway. Only teleport back to beginning?
Back to teleport maze, examine remaining options. Nothing new found.
South to violet area. Lots of rocks lying around, to throw on plates?
Jump into pit to see what's below. Complete darkness, can turn but nothing to see or do. (No room under pits?) Have to reload.
Throw rocks on plates to open door. On approach door closes. Timed or triggered by plate? Bet on timer, throw more rocks and rush through. Except plates already pressed by previous rocks (duh!), so no effect.
Secret button in corridor, find leather brigandine.
Can't find way through door, visit large SW room again, red gate open (red area completed?), get key.
Open east door with key, get red gem. Try placing on entrance corridor middle alcoves, first east then west. No effect.
Back to skeleton room, kite some back to corridor and down the pits, more keep appearing. Killing skeletons still crashes game. Jump down to pit, find skeletons & herders, get slaughtered.
Restart level, go to violet area, throw rocks and rush through door. Success! Earlier timer theory apparently correct. Is there a way through after failing once?
Room with pillars. At SW corner, turn north, step east, crash with message "[string "Teleporter.lua"]:0: attempt to index field 'map' (a nil value)"
Crashes keep happening in the room. Clear path exists? No obvious marks, don't want to try blind when every misstep requires restarting the game. No way back since door closed.
Restart again, go past teleport maze and try ordinary button first. Same effects as last time, meaning of message still unclear.
Explore trapdoor corridor. Below, confirm that more snails appear as previous ones killed. In other rooms crowerns and small herders.
Above, notice that on faster trapdoor toggles animation glitches a bit, open starts before close finished.
Find secret button and scroll.
Can't find anything else to do with two areas unstable.
To summarize the worst issues: crashes at skeletons and pillar room, getting stuck in pits in violet area, possibly getting stuck in same area if first attempt to get through door fails.
Other impressions:
Different areas have been placed quite far apart and given more than minimum space. As a result, the level has a distinct feel compared to the usual cramped corridors.
Balance seems to be ok. The combat and puzzles I passed weren't all that difficult, except for the rooms under trapdoors; fighting multiple enemies in small space is always more challenging. The skeleton fight will likely also be tougher, and I can't yet say anything about the pillar room puzzle and beyond.
Personally I don't much care for respawning enemies, but I guess that's a matter of taste. You might look into ensuring they don't just appear out of thin air, though, at least when the player is looking. Unlimited XP gain might also be problematic, though it can probably be dealt with.
Equipment could be handed out more generously, though of course there might have been more that I missed. Food is plentiful.
I also noticed that found secrets don't show up in the statistics, they kept showing 0/3. You need to activate the secret object to update statistics, it also plays the secret sound.