I have several scripts to automatically restart and save the server. If a server save is initiated via save-all, and the server is shutdown quickly after, the server stalls at:
[01:12:13] [Server Shutdown Thread/INFO]: Saving players

The issue does not occur if the level was not saved within ~5 minutes before hand.

Only way to shutdown the server is to forcibly terminate the process. CTRL + C does nothing to shut it down.