It throws a message saying "You're trying to spawn the minicopter to far away" when it should just despawn it.

See https://umod.org/community/spawn-mini/21562-commands-show-the-minicopter-is-too-far.

same issue for me and the link wulf posted does not help as i dont even have that option in config file
typing /nomini should remove the mini

For some reason increasing maxnominidistance in the config fixed it for me.

It shouldn't show the message "You're trying to spawn the minicopter to far away" that must just be an error.
I thought setting it to 0 would make the range unlimited but I didn't, I recommend just setting the maxnominidistance to a very high number.

Delete the config and reload the plugin your config might be outdated