1) Yeah, you are right about the changing direction. I think the hole was in the x direction. That also fits with my observation that when I pluck the front x belt the frequency is about 310 Hertz ( I'm assuming that this means it is too tight?)
2) When I gently push the nozzle of the printhead in any direction it isn't moving. When I'm moving the whole printhead it is in sync with the stepper movement.
3) So after I eliminated the play on the axles it got a lot better. But still, there is a small imperfection. The imperfections are only on the layers where the hole starts and ends. I will wait if you can say that the front x belt is too tight and then try again. If the issue still is the same I can send you more pictures if you want.