The server crashes due to Simply Jetpacks 2. When I remove the mod, everything works perfectly. The server log and crash log are attached. I use version 2.2.20, but older versions don't work either.
crash-2021-08-03_15.31.38-server.txt
latest.log

fairly sure this has something to do with stacks of some sort, not too sure at the moment.

The fix for this is mentioned here now, hope this helps 🙂
https://github.com/Tomson124/SimplyJetpacks2/wiki/Common-Issues#server-crashes