Well, today I woke up like this:

Nah, I have an old black & decker rotationsander, but it looks like that sandpaper was too thin for that machine and it got damaged after 1 minute or so.
Then I switched to hand sanding to do something at least. Today, I put some duct tape on the backside of that sandpaper and will try it again with the machine. If that doesnt help, maybe I will order a new machine.
About that defender, did you cut off the bottom of the cab and put some new wood panel into it?