DaemonUmbra

Again this error seems to come down to an issue with the game being unable to write to a file, apparently because another program has it open. Your server's not in a folder monitored by some kind of file sync program, is it?

Where are you getting your mods?

It sounds like one of your mods needs JEI installed on the server to utilize certain features

Please define: "it" "this" "something" "it", and "it"

1.8.9 is no longer supported on this forum due to its age. Please update to a modern version of Minecraft to receive support.

Not a debug.log and according to this you're only allocating 2G

Please provide debug.log from the new run

That is not a debug.log from the server, and again I see nothing about your client acknowledging a disconnect from the server

There's still a server running, it's just one that only you can access. and my point stands, this is not something breaking, it's your game needing more memory.

Nothing's breaking... Your server is just doing something new that requires more memory than it did before

I'm just interpreting what the log says, if the game itself says it's out of memory then I can't really argue.

Well your game ran out of memory, so try giving it 4G.

RAM In general: Memory = RAM Storage = Disk

How much memory is in your machine?

Try this: https://johann.loefflmann.net/jarfix

That's not a log, that's copy/paste from the launcher's console. Please provide debug.log from your .minecraft/logs folder

You need to use Java 8, 9, or 10

1.7.10 is no longer supported on this forum due to its age. Please update to a modern version of Minecraft to receive support.

Why do you have Both NotEnoughIDs and JustEnoughIDs? Why do you have both Veinminer and Ore Excavation?

You are trying to access client-only code on a server...

What launcher are you using? Please provide a screenshot.

Warning: MCreator Cruft

User was banned for using a cracked launcher. Buy the game.

Please read the Logs section of my signature below and provide the appropriate log in the appropriate manner.