For some time now, the servo that's used to switch between the 1st and 2nd extruders is acting up: during various phases of a print (especially homing, but also while printing/extruding with the 1st extruder), the second extruder is erratically moving back and forth between its two end positions. Sometimes it's twitching once, sometimes twice, sometimes a dozen times at a time, then after a few seconds this repeats ... or not. Astonishingly this only ever happens when the second extruder is not extruding. Still, it's somewhat annoying.
I guess it may be a bad contact or broken wire somewhere that's disturbing the PWM signal driving the servo. Is this a known defect? Where are the relevant connectors or cables that I could check? Are replacement wires available?
Any input would be much appreciated!