The best example of how to crash the server it's to explain how to do it !

1) Disable the Vanilla datapack (see picture1)
2) Looking for a secret place (see picture2)
3) Teleport you to this place (see picture3)
The server crashes, the players are disconnected. (see picture4)

4) Restart the server
5) Connect to the server
The server crashes, the players are disconnected.

( See latest.log )