914 servo motor chatter/buzzing

Hello.

While troubleshhoting the engine for suspect airbox pressure sensor malfuncioning i hear (on the ground with stopped engine a chatter / buzzing sound coming from servo motor that moves wastegate.

Connecting Rotax TLR diagnostic software it show that servo position varies continuously by1/2 % , in parallel with the fluctuating noise. it seems "hunting" a position.

The chatter is continuous and do not change with throttle movements  (from idle to max)  which varies wastegate position.

I suspect servo motor connector or internal potenziometer (wiper) problems. 

do you have experience?