The server crashes everytime I send a command /febutcher -1 HOSTILE in the Nether.
I don't know if it has something with the Nether or not. (I'm too afraid to try it in the Overworld)
In case it may help, the first time the crash happened I was in the Nether and I did /febutcher 500 HOSTILE. I didn't wait for the command to print anything in the console (thinking it wasn't working because it took more than 10s) and I did a /febutcher -1 HOSTILE. Then a crash occurred for the first time. (The command worked fine before but I never tried in the Nether, it may be the issue.)
Now, everytime I try a /febutcher -1 HOSTILE the server crashes.
I'd be glad to give you the logs but I don't know where to find them.

I can not help you unless you post a crash report.

Look in ./crash-reports

The folder is relative to the server root folder. It's a sibling of the ./config. the ./forgeessentials. the ./mods and ./world folder.

In that folder you'll find crashlogs in plain text format. Upload the relevant crashlog to pastebin and post the link to that paste here.

DO NOT paste the crashlog here, just a link to the log.

Alright, I think I found the proper one: https://pastebin.com/V2ZbD3vR

You can help me by telling me where I can find the crash report. (This is on a multiplayer server, by the way)

I'm not seeing this one...

As we moved to 1.12.2, is this still an issue? Closing this issue in 7 days if no response @Telokis