Problems with Servotronic

Hello, everybody! The following problem: If you turn about 10-20 degrees to the right during the ride, it will be as easy as it is in the stand. To the left, everything is OK. You notice clearly when you move the steering wheel, how after a very short time the corresponding back pressure is built up by the hydraulics and the steering will be "straff" again as it should be. I could also determine that this phenomenon only occurs when the hydraulic oil is warm. Everything about hydraulics I have already replaced with new parts. I changed the steering for leaks two years ago. Also the pressure storage system all pipes, hoses and lastly also the hydraulic pump because of the above malfunction. I imagine that despite all cleanliness and care some dirt / small impurities have come over the oil in the rotary pusher of the Servotronic and there for this fraction of a second a valve clamped.? Who has had such a thing before and what was the cause? Of course, it cannot be ruled out that the steering gear has made the "Biege" after 2 years (rotation pusher/valve unit). Happy greetings to Matthias