I noticed my copter tilting backwards, while it's leveled correcty. So it needs correcting all the time while flying. But now I have an idea what's causing the problem. The ESC that's controlling the motor on the back is getting more hot than the others during normal load, the difference is significant. There is someting wrong there... The motor doest NOT get hot.
My setup can be seen as 'standard'.
So faulty ESC, any ideas?