PC 330 Motor problem

I bought a PC 330 a few years ago. All I have heard on the newsgroup has been good. I must have gotten the one lemon they produced.
About 6 months ago the clamps that hold the paper developed fatigue cracks. I got the parts, but it looked like putting them on took a gorilla with four thumbs. After long discussion with a PC tech, I got that problem resolved. - It is no easy task to replace them!
Recently, I have noticed that the motor keeps slowing down to about 1/2 speed and then going up to full speed. It only happens when I place the sander on a piece of wood - no downward pressure applied by me except to hold it on the wood. I checked the connections and brushes; they seem to be OK. Anybody had the same experience; what's the cure?
Thanks, Len
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My old one did this and had the broken springs that I replaced. It was about 15 years old and I replaced with the same sander. I can only say that they don't build them like they used to. I was never really impressed with the newer same model. A couple of years ago I replaced it with a Festool.
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