Right belt imperfect

Hi all

Need help to a NOT solved problem with a new used Board.

My belt the moving either outward or inward on the motor gear dependent on direction on the board. This was only a problem on right site (with the new rear strut), therefore I change the rear strut to a 2nd new on, and It only became worse: now I have the problem in both site (with opposite result the belt go outward on the motor gear when driven forward og go inward when driven backward). So I change to first new rear strut, and now I was back to the old problem again (only belt problem in right site). I also tried to change gear, belts and motor hangers but withe same result. So my conclusion is: different rear struts create different problems as described. I have also separated and assemble the rear many times, and the result is just the same (no matter what I do). What is the problem? Motor or strut? If it was the motor axle I will get the same result with different struts , and that’s not the case immediately!? What do you think?

/TOMMY