Fired up a test server using the 18w47a Snapshot.
When I stop the server, it won't fully stop. World saves, and it just hangs there.
I let it sit for a few minutes... you will see in the picture the time it "stopped" at (19:00 / 7:00pm)and the current clock in the corner ( 7:05pm). 5 minutes and nothing happens passed the world save point.
Environment
MacOS 10.14
Java:
java version "1.8.0_191"
Java(TM) SE Runtime Environment (build 1.8.0_191-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.191-b12, mixed mode)
Startup command arguments:
#!/bin/bash
cd "$(dirname "$0")"
exec java -jar server.jar nogui
exit
The same with 18w47b.