A6 c6 auto gearshift stick stuck
 

Hi guys, I have an Audi A6 C6 2.4 FWD pre-facelift with issues regarding the automatic gear shift lever. It gets stuck in parking. I have rectified this twice now using the method where you press something in the ashtray but I need some help diagnosing the root of the problem. I can find this temporary solution to the problem but there isn't a clear answer as to what is the root of this issue.

the brake switch did give a problem a while back one where the brake lights stayed on but that problem never returned so I assumed it was fixed.

The car has done this twice now both times it has been related to reverse. First time after reversing and putting in park the gear stick got stuck, second time reversing up a steep hill, I heard a cracking sound and the reverse gear seem to become disengaged as if no power was going to wheels, Following this put the car in park and again gear shift lever was stuck in park. First time the EPC light did come on but I did not have my code reader and second time EPC light didn't come on so I don't even have an error code so I don't know if it's related to a bad F125 switch. Can you please give me some advice as to how I can diagnose the problem? Thank you, your input is much appreciated.