PDC defective ?

hello… for months the PDC sensors only work sometimes on my evoque. I start the car after a night in the garage, the sensors work both front and back and I get the obligatory beeping with the bar display to the camera image, sometimes only the hint the camera and pdc don’t work and still see the image of the cam and sometimes comes still the hint, I would like to check the environment on objects… all this is not bad anymore and I don’t care insofar as I’m driving anyway after mirror and backcam, nothing has happened yet. the problem is now, I want to sell the evoque. the reasons for a vehicle change are different in nature and should not be discussed here… I noticed the following: if the pdc doesn’t work, then the P button on the MM system flashes 6 times in a row. if it works again, I didn’t notice any interval. every 4th or 5th. cold start there is a rather long beep tone and does not appear another hint, the return cam always goes… I had a look at my workshop before the last tuev in Januar, who did not notice that now…this one has mentioned in my presence the diagnostic device plugged in and there were no errors in the memory displayed. so I exclude a mistake on the control unit. when one of the sensors is gone, or a wobblekont act, why does the pdc work sporadically at the front and at the back and sometimes not ? it sometimes seems to be “overriding” by inserting the backward passage when ignited and suddenly I get the green or red beams and stay even when I start the engine, after a short break I repeat the process without the “only ignition trick” and it twitched around again… what can it be? a potential buyer has noticed now and it naturally makes itself bleak d, if you can’t give an answer…