Telescope Reviews: Problem with ALT motor??

Hi,

There is an issue with my CPC-925 alt axis engine. As a matter of fact, the issue has been building up almost unnoticed over the last few months, but last night I had a real problem: the scope was unable to slew up or down at higher speeds (higher than rate 6)
Tracking stars still functions perfectly (I took pictures from 20:00 until 03:30 and most of the 30 second subs show very nice point-like stars), but manual slewing or using the goto was a disaster.

Manual slew at rate 9 was extremely slow. Most of my gotos failed as they also were anything but smooth.. During goto, the scope even stopped for approx. 30 seconds and then resumed for a couple of times... until it gave up or went nuts and kept on drifting.

Today, I started with an investigation and here are my main conclusions:

1. the issue is temperature related: the colder it gets, the more pronounced the issue becomes. Last night, the temperature went down to -5°C = 23°F. At the beginning of the session, slewing in ALT was slow, but still doable... At 03:00 it barely moved.
This noon, when the scope was indoors nice and warm, slewing was back to "normal": there still is a speed difference between slewing in ALT or AZ.
AZ always is swift and smooth. When you release the button, the motor immediately stops.
In Alt, the movements are slower, the motor does not make a consistent smooth humming noise (there sometimes are some small hiccups) and if you release the motion button, it tends to continue for another half a second.

2. I measured power consumption of the system by putting a current meter in between the battery and the scope. When I activate the AZ-motor at rate 9, it draws about 0.4-0.5 Ampere.
Activating the ALT-motor makes the system draw about 1.4 Amps... It looks as if the ALT engine is under heavy load as it draws 3 times more power.

3. The current measurement was done with both clutches disengaged, so there is no reason to assume that scope unbalance or bad clutch coupling is the cause.

4. I connected the NexStar handset to the AUX port, and the result is the same.

5. At night I also did a factory reset, so we can rule that one out.

6. I also swapped power sources: Powertank and DC regulated Power Supply.

What now? Where should I focus my further troubleshooting steps on? Your help is very welcome!!
Of course I am aiming to avoid shipping my scope back to Celestron... we all know this means I will be grounded for months then. I have been a good boy, so I don't deserve that!

Thanks!

Koen.