Hi, I tell you how I solved this troubles if it can help... I have had garbage on the screen so I shortened and shielded cables, it solved screen troubles but then I had the "strange movement while printing" as described by Scubi... For safety reason, earth AC wire ( the yellow/green one ) is connected to aluminium frame of printer. Earth is also connected to GND (or 0V ) inside the switching pby titi67 - Firmware - Marlin