CMM1200 stalls under light load

I just bought a used CMM1200. The seller warned me that it works perfectly but stalls without being overheated.
This was an honest assessment.

It stalls after maybe 5 minutes of use, then stalls more frequently after that.
After waiting about 30 seconds each time, it starts right up again, but then stalls.

I am thinking there must be a sensor somewhere that is bad.

Any suggestions?