disconnected, server crashes on reconnect. - JDK version related?

Shortly after trying to attack a skeleton, bad things happen.
Arrows go schwee, mobs freeze and about 30? seconds later it disconnects.

On attempting to reconnect, the server crashes:

[15:01:31] User Authenticator #2/INFO: UUID of player Usagiyahara is 466ecee3-f34a-4c02-a752-0aff215f7ee4
[15:01:55] [Server Watchdog/FATAL]: A single server tick took 60.00 seconds (should be max 0.05)
[15:01:55] [Server Watchdog/FATAL]: Considering it to be crashed, server will forcibly shutdown.
[15:01:55] [Server Watchdog/ERROR]: This crash report has been saved to: /home/minecraft/./crash-reports/crash-2019-05-02_15.01.55-server.txt