In 1.16.1, Entering the final end portal crashes the whole server. Tested with 4.1.0
Log: https://pastebin.com/4f4J5unT

As far as I can tell from this error there isn't a mention of a plugin in the error so this might actually be a bug in your server software which you might want to report to them.

The issue persists, at first when going through the exit end portal, it spawns inside the nether portal in the world instead of spawn(e.g bed), after trying to change the spawn it now crashes the server. Log: https://pastebin.com/tmr1Z9LJ

Currently, the server is hosted on Shockbyte, I have opened a ticket with them, I will download the server and try hosting on my personal rig to confirm this.

I have solved the issue by resetting the plugin files, yet now it respawns me in the wrong location and not the world spawn.

Whenever I go to The End by going through the End portal, it creates a Nether portal once I arrive, that's what the issue was.