Caldera Spa - Air control valve troubleshooting

[TR Nolem]

Feels like it should be an easy fix? 

Background: Caldera Marino 2020 model. The "air control valve" pictured stopped functioning properly a few weeks ago. It typically feeds air to 13 jets across 3 seats (corner), but now only adds air to 2 jets, one each on the non corner seats. 

Troubleshooting: I've pulled out the valve, swapped with another valve from a working side, and it still is not working so the problem seems to be internal? Valve pieces from different sides seem to have no visual differences/defects, it's a very simple mechanism. Also, when I have the jets on and remove the valve entirely, air flows to all of 13 jets, so nothing is blocking or stopping the air outpur from what I can tell, but could it be wherever the valve pulls air in (source air)? 

Additional: I opened up the side of the tub where the valve is failing. It's loaded with blown-in insulation behind a very thin cardboard. I am reluctant to remove/dig in the insulation as I would be unable to restore the "fluff" of the blown-in effect, reducing my overall heat insulation before a quickly approaching Illinois winter. 

Called repair company, crazy expensive just for diagnosis. 

Any suggestions for additional troubleshooting ideas? The system seems very manual/mechanical, but could it be a problem with one of the two motors or electrical? It's worked fine since I bought it 4 years ago.