Tried with builds #47 and #48, TFC only mod on client and server.

When trying to start a fire in a firepit, player is disconnected because of an internal server error.

Log attached.
Java error on pit kiln.txt

Full log please, not just what you think is the relevant part.

Actually reproduced this morning on client, with a fresh build 48 installation. Logs attached.
Logs - Firepit crash.zip

With server crash log attached.
crash-2019-08-12_10.28.42-server.txt