Oh nevermind I found the issue. I accidently left my aircraft on some inserter which then inputs into the aircraft and when I left it on inserters pulling out it then messed the belt up. Thanks anyway.

An belt (Fast transport belt) with iron plates runs directly next to a belt (Fast transport belt) with copper plates and there is no chance the two merge somewhere. But after some time I notice that there are a few copper plates on the iron plate belt. Installed mods: Aircraft Aswil Better long hand...