Thanks guys for all the feedback, I really appreciate it. I think I will try to remove that steel bracket that is on the trimmer which is what I suspect is the one causing the problem, after that I will get a good cutting matte and sharp knives and do it that way, but my experience with that is not without issues, in particular then you have used that matte a bit, and you get cut marks in it, the knife will sometimes follow an old cut, and it may not always be as you are currently cutting :-) alternative is to cut on glass and change the knifes more often.
thanks
Henrik