I first re-coded the door locks from 15887 (factory setting) to 15983 and it defaulted back to stock a day later, although the code still showed as 15983. So I re-set the code and it kept it for 4/5 weeks until yesterday when it happened again and defaulted back to stock. Any advice or observations as to why????

Specifically on the control module that controls the locks.

I just have the dealer to Vag my 03's. So far no problem yet for 2 days.