We are having an issue where a LAN player is getting disconnected when they die. There isn't any error in the logs or the console but Open Blocks is trying to save items to the grave files. Is there anything we can do to try to figure out if Open Blocks is the culprit or some other mod? Is there a log that I don't know about?

Disconnects usually leave at least minimal logs on serving side. Have you tried to check fml-client-latest.log on both sides?