Just as a follow-up, I tried repairing core files and that didn't work.
However, I reset the server again and that did work. The server is working again.
After playing around with it a bit, I found out that it may have something to do with the fact that I was trying to generate a Superflat world as my default world. I don't know if the world generation features on Minehut are bugged (or even if this is a known bug or not), but from what I found while testing, that was likely the cause of the glitch.