Claus Rieper, as you already know the UL error is an unbalanced load error. Since it happens even with an empty washer it sounds like the problem is the rotor positioning sensor (RPS). [http://www.repairclinic.com/PartDetail/Rotor-Position-Sensor/W10178988/1668992?modelNumber=MVWB400VQ0|This is] the part you would need. Here is [https://youtu.be/KTBb-hTkq1w|a video] that at 3:09 shows the location of the RPS. Hope this helps, good luck.