[Latitude 28]

I had almost the same thing going on with my 120v air compressor but the opposite problem.  The 120 air system would gauge would go to zero without the compressor running.  Then on its own without doing anything with the system it would start working.  This happened on several occasions without any warning.  Suspecting the pressure switch I order a replacement....https://www.amazon.com/gp/product/B0078RSLAY/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1.  Changed it out and inspected the old one....the diaphragm was full of rust and crud.  Probably what was happening the rust and crud kept the switch from sensing low pressure that would turn the compressor on.

Having said this,  If your diagram has any crud and possibly a hole in it that gets uncovered in the low pressure ranges but covered up at the higher pressures could explain what you're seeing.

Steve