It started with a player on my server getting kicked out every time he went through a nether portal. Then, yesterday, the server started crashing whenever he went through the portal. Now, it crashes when he signs on.

I have posted this already, but it was dismissed as a "get a better computer" problem.

1) That's BS; it was playing just fine with 3 players before this issue arose.

2) I've increased my RAM to 32 GB (and increased the server starting RAM to 2GB) just to prove that that's not the problem, and it's still happening.

3) It only happens for this one player. 

4) I realized that the watchdog was shutting it down due to it effectively freezing, but I was quite certain based on the things listed above that it wasn't just a computer resources issue.

5) If you look closely at the crash reports, you see stuff about locks in all of the worker threads. I think there's a deadlock happening.