I think #1023 needs to be re-examined. I've added my notes there.

Essentially, when doing anything with the shulker shell, a crash to desktop happens, and you cannot do anything with any inventory after the fact. If you select anything in your inventory, and this crash happens, you lose that item as well. Disabling Quark seems to be the only way to get back into game play.

I also went so far as to revert to a previous backup of my playerinfo files, and with Quark installed, I STILL get a crash to desktop.

I went and restored a world backup, got back in and got to a save point from last night (Only about an hour out from where I was). I noticed I had Shulker Perls in my inventory. The second I clicked on them, I got the same crash. Re-doing my world and trashing these items.....

EDIT: To note, the crash seems to happen when I just LEFT-CLICK on the item. If I CTRL-LEFT-CLICK and the busted item goes into a different inventory, I don't seem to have a problem.

I'm having the same issue (I have the newest AutoRegLib, and the curseforge Quark).
https://paste.dimdev.org/hadesihuge.mccrash

That is not the same issue.