Problems with the MDI device

Has anyone had any problems with the MDI system? Has worked brilliantly for the first 6 months and then started to die. I suspect the cable is goosed but every time it goes into the garage they say it works.

Thing is, it works when you plug it in, then as you drive it looses either the files, or the ipod all together, or plays one track on a loop or it wont auto start the ipod after a phone call (I have to lean over and press the play button).

It does this on my classic, my iphone 4, the wife's 4s and my brothers nano. But not apparently the garage ipod. I bought a cable of ebay but i think its a Chinese copy. Just bought another genuine skoda cable to see if that fixes it but its very annoying