Same thing happens to us. Also funnily only noticed it recently, and had a service at the dealer in March.
We had the sticking buttons last year and Vw say that they have replaced the panel. It definatley fixed the blowers being on when starting the van. Looking at the panel now the buttons don't appear to be sticking. I'm questioning whether it was replaced or whether they did a quick fix as our rear heater has now developed a mind of it's own.
Last couple of long trips, after roughly an hour (could be coincidence) it starts. Heater come on full power and heat and won't stop until it's turned off from the dash, either by using the dial or pressing sync. Turning it off doesn't work as it just fires up again shortly afterwards.
It's happened today, again after an hour or so, so I've pulled over to investigate. On the rear panel pressed the auto and off button. Both worked for a split second and then it went back onto high. The only way I could get it to stop via the rear panel was by pressing the down arrow until it went off. This seemed to solve the problem for a few minutes but then it just started again.
This is the first time I've properly investigated the rear panel during the malfunction. I was surprised that the hot air isn't actually coming out of the rear panel vent, but the vent on the rear door pillar. This explains why others who've had the same problem report that unplugging the rear panel doesn't fix the problem.
Gonna take a video next time it happens, and get the van booked into the dealer again.
