Window controller (but not) issue

Ladies and Gents,

Ok, have one for you here that I was looking for a bit of help with.

The other day both windows failed at the exact same time (one in the down position). Just before they failed I noticed that when I opened of closed them they would hit the stops with a bit of a force, making me think something wasnt right. They then failed. Interestingly enough when I pressed up on one of them it went down. Pretty big fail. I also noticed that the radio would run with the keys out, im sure it didnt do that before.

Being an engineer, I thought that the problem must be exterior to the commonm elements of the windows as they both failed at the same time (if both controllers failed on their own just by chance at the same time I would be more than surprised....). But when I took it to the garage they rather hasingly said it was the controllers and they replaced both of them, which I was convinced couldnt be the problem (something must have cause them to fail, they wouldnt just fail on their own at EXACTLY the same time). Never the less, we paid our 500€ and went on with our lives. This was only a few weeks ago.

Until the other day when the windows started hitting thier stops in the same way, indicating something once again wasnt right. And then yesterday something very exciting happened which was when trying to adjust one of the mirrors they both moved, one up and one down.

So I want to go back to the garage to get them to do it right this time but I need to tell THEM what the problem is. So does anyone have any idea? A voltage problem? It must be something that is exterior to the windows that is causing the failure of the controllers or something. A power problem of some sort? Any ideas?

Any help would be greatly appreciated. Just for info, its a german build Mk II (I live in Germany).

Many thanks chaps!