While checking the console for info after experiencing a long lag spike (which probably has nothing to do with this mod), this error message was reported-

https://pastebin.com/fwKvnmkU

Looks like i might have forgot to add the loot table for the bound soul.

I just got this error on an MC Eternal server (latest version of MC Eternal, latest version of this mod too I believe). Same thing, a very long lag spike while fighting some of the tombstone souls, and then I saw the error message. What's more, I had dug down to find a moldy create with Iron Lock, and tried to unlock it, I think during or right after the lag spike. I got the message "key broke", and when I checked my key ring, all the keys had been deleted. On the key ring I had one of every key plus a couple duplicates, all pretty much full and with Unbreaking III enchantments on them. I had only attempted to open the chest one time. I even tried logging back in to see if it was a sync error, nope all the keys were completely gone from the key ring. Only solution was to restore from backup to get all my keys back.

To see if this was a reproducible situation, I went to the exact same chest after restoring from the backup, and attempted to open it again with the same key ring. This time, the iron lock opened just fine and I could get into the chest. Also, I didn't get the lag spike or the error message the second time. Don't know if that helps with any debugging, but wanted to report what I experienced.

Thanks!

Thanks, any and all info is helpful.

Fixed the error as reported in the pastebin capture for v 1.11.0. Not sure what the lag spike is about nor the keys disappearing (that is probably a separate issue).