using the latest version of hoppers plus for forge 3.3.1, placing hoppers in unusual orientations causes a game or in this case a server crash.

i removed the mod so the server could restart and then reinstalled the mod (note that without removing the mod the server will crash upon trying to re start).

if needed i can send logs for further troubleshooting. as far as i can tell the problem is purely related to this mod but i am unable to confirm it.

note i have seen this in both single player and multiplayer worlds