No way to prove it but I'm leaning toward Raymarine having made some poorly-engineered or cost-cutting changes when they built their own brand of motor drive to replace the venerable AutoHelm drive that was part of the AP wheel system they bought from AutoHelm.
I had an AH 4000s wheel drive that was quiet, except for the soft whirring of the motor, for over 15 years. Due to "old age"... I stupidly replaced the whole setup with a new A-5 system a year ago.. So far the computer unit and display have been back to Raymarine for repair and it works better now, but still stops and drops our of AP function once in a while, or refuses to go to AP function until you tap the button several times.
Our wheel drive unit makes a loud screeching noise (like plastic rubbing on plastic) most of the time it operates. It does not slip, but you can hear it clearly over the sound of the diesel!
And this is After
it also was checked over, under warranty, by Raymarine
I really wish that there was some competition for this product, but other than the "Old School" CPT unit, there isn't. Despite the excellent reputation of CPT, we wanted an AP that would network.
Best of luck with yours, and with Raymarine.