[Richard]

Ask the technician to dead head the compressor before the check valve. The assumption that the check valve is closing prematurely doesn’t sound right. First, the closure direction of the check valve is opposite the flow of the air, and second the normal check valve failure is that they fail to close.

Dead heading the compressor will isolate the problem to the compressor or the pressure switch. If the pressure switch is observed during a cycle, then it is easy to tell with the cover off, if the switch opens.