I have three Aiwa Micro Systems like yours, the XR-M25, the XR-EM50 and the XR-55U. Two of them have the same problem as yours and I'm trying to figure it out. I got the service manual for the M25, but it has no troubleshooting guide. I suspect it's the motor which is actually a Sony part. Check for Sony units that have same problem. Please post if you find a fix.
Len Reinsmith, August 2006