I am seeing this as well with both this version of the mod and the one on nexus (Magic Grimrock 2-60-3-3-fix.zip). I get a certain distance into the game and then my saves fail to reload, giving the following error:

=== Software Failure ===

[string "Surface.lua"]:0: could not resolve object reference with id 48527 (referenced by chest_2b)
stack traceback:
[C]: in function 'assert'
[string "Surface.lua"]: in main chunk
[string "GameObject.lua"]: in function 'sendMessage'
[string "Map.lua"]: in function 'sendMessage'
[string "Map.lua"]: in function 'gameLoaded'
[string "GameMode.lua"]: in function 'loadGame'
[string "GameMode.lua"]: in function 'update'
[string "Grimrock.lua"]: in function 'display'
[string "Grimrock.lua"]: in main chunk

In my last game I was down in the twigroot tunnels, the first area where you find the whitewood wand, just next to the pit trap. I saved there, then on reload I got the error and the game crashed. This was with a fresh game with newly created characters (no imports).

Hello! Sorry for the late reply.
This bug will be fixed soon in the next update. Until then, let me tell you how you can avoid it.

This is linked to the quick bars next to characters portraits. If you pick an item with the mouse from a chest, an alcove or an altar (every surface except the ground), and switch it directly with an item in the quick bars, your game will be corrupted and won't be able to load from this point (the surface will assume that it contains the switched item, but does not). So if you still have a save that loads, you can avoid the crash by dropping your items in your inventory or in empty quick bar slots instead. If you wish you could also send me your corrupted save game file (egraynn@hotmail.com) and I will send you back a clean file. :)

New version 3.4 available, with this bug fixed :)

I still get this error message ;~; just subbed today

Do you really see version 3.4.1 in the Grimrock menu? Do you use an old save?

I realize this is very old, but I'm getting this error as well and may have found the problem/solution. I think it's related to specifically the Power Gems for the Fire Essence. I think it might be specifically the "Be Quick" one. If I obtain that one and save, the game crashes on reload.

If I place the Be Quick one on the Fire Essence altar, the sequence that creates the Fire Essence immediately begins even if the other three Power Gems aren't on the altar. Then the game crashes instead of spawning the Fire Essence.

The only way to proceed smoothly I found is to leave the Be Quick gem where it is. Place the other 3 gems on the altar as you find them, complete the whole Twigroot area, save, grab the Be Quick gem, place Be Quick gem on altar. Fire Essence will now properly spawn and you won't be in danger of crashing anymore.

Thank you ! Very specific problem you found here. Not a clue for now how it could be related to the mod, as it does not change anything about power gems, but I'll investigate !