Sounds like everything works perfectly, except for the shutting down part.

It could be a safety switch that opens and shuts down the machine - maybe the compressor is overheating (screw element outlet temperature)? Although most of the time, that only happens when running loaded.

Any indication? Alarm light, etc?

It could also be a loose electrical connection. Does it shut down always, and around the same time? Or does the problem come and go and happen at different times?

Hope this helps :) Ask more if needed :)

Thanks, Cas