So it all started on saturday, I was seeking through a long mix on the car stereo, when suddenly the button for "forward/next" stops responding. Since monday was a holiday, I decided to try fixing it myself. It took a good part of five minutes to finally open the front panel, because beside the four screws, it was also held in place by numerous small plastic hooks which I had to bend. But after finally opening it, it was obvious that the problem was easy to solve: a small plastic bit broke off from a four-way switch. I cut off a strip of plastic from a fridge container box, and superglued it to the switch.
Needless to say, it didn't really work. But at least I was able to change tunes one out of three times.
So on tuesday I was heading to Dension's service shop, expecting my warranty to be void: bear in mind that it was painfully obvious that I opened the unit, because there was a frickin' bit of plastic glued to one of the switches.
However, this didn't even come up: first they replaced the switch in question, then it turned out newer units have a slightly paler button design, making the replaced one stick out. So at the end I got a complete new front panel. All this taking less time than my attempt at fixing it myself.