Server crash after last player left

Last player on my server left the game normally, server was working fine while he was connected. After that, the server abnormally crashed.

Used datapacks utilise minecraft:tick. They are from vanillatweaks, downloaded for version 1.14.4. Haven't had any problems with them, in 1.14.4 nor 1.15.

I've replaced all instances of the same player name with *Player* for anonymity in the server log and crash report.

What I expected to happen was...:
After the last player leaving, server normally idles.

What actually happened was...:
Server crashed because a single server tick took 60 seconds. The times in the log file are all mixed up.

Steps to Reproduce:
I've been unable to reproduce this bug.