Users report:
Uh, I'm selling 2304 coalblocks to clarinet at -437 68 243 but I have literally 0 coal blocks in my inventory?

Errors:
https://pastebin.com/8pgZy65p

I've verified it all. TL;DR you can sell to chests without having the actual items.
Rolled server back a few minutes and reverted to build 129. No big deal, I like to fiddle with dev builds, what can I say. Thankfully caught it in just a few minutes, any longer would've been an ooooof.

EDIT: After rolling back to build 129, all is fixed :)