I was able to repeat this crash multiple times. I have a villager in the Trader block from the mod that is a novice cartographer. I traded him enough paper to try to level him passed novice and once I do that, the server stops responding, disconnects me and ultimately crashes. I start the server and in order to connect back to the server, I have to completely close out the launcher and restart it from CurseForge.

I have a similar trade of 19 paper for an emerald with a librarian villager. I tested with that villager and I am able to progress it beyond novice without the server crashing. So it only seems to be an issue with the cartographer.

Crash report: https://pastebin.com/MnXTddzj