Electric Window problem

Hi all. Ive just bought a 2002 Superb and have already had to sort out the usual water/wiring problem. Now its time to tackle the next one. The problem exists around my drivers side rear door. The central locking feature doesn't work ever. The window didn't work at all then I replaced the motor et al with a donor part from a passat. This was tested on the donor car before i bought it and it worked fine. Eventually I traced a broken wire in the loom between the door and the B pillar. Now this is where it gets interesting. When I connect the wiring to the window motor it works fine. Actually, it works too well. It will work without the key in the ignition. Give it 10 minutes or so and it stops working. Disconnect at the motor and reconnect again and it works for another 10 minutes. I've run out of ideas or options so need help!

Also, the passenger side window has started playing up now. When you control it from the door switch it is perfect. Try doing that from the drivers door control and it stops and starts throughout the cycle. There's no pattern to the stopping. Sometimes it stops 10 times, sometimes it stops 20. I've replaced the drivers control unit/switch but no change.

I'm considering lifting the carpet again and seeing if there is another bunch of wires with problems. Given my 100% success rate with my courtesy/puddle lights I may be right. Or I maybe wrong. Does anyone know?