New Tekkit Classic Server Crash

[Toasti3s]

I was trying to start up my Tekkit server when I got an "Exception in server tick loop" error
(full error here: https://pastebin.com/2eBy6URK)

This has happened to two different servers of mine. The servers will start up and work perfectly fine.
If I shut the server down the try to start it back up again I get nothing but that error.
I can't find any solutions on how to fix this problem. 

Thank you for any help!