QT dash switch

[Curly]

So, I pulled the front driveshaft, put the jeep in E-drive and drove it to check for vibes. Reinstall the d/s, go to switch back to normal and the tcase wont shift. Turns out the normal position of the valve isn't working. E-side is, so swapped hoses to get out of Edrive. (worked )
So, my question is: can the switch fail in such a way to lose vacuum on only one side? One side has strong vacuum, the other has little to none. No hissing sounds under dash, switch worked last time I tried it, 6 mos ago.
(This is the dash switch, not the one on the tcase.)

[fulsizjeep]

The weak steel/rubber vacuum line could be clogged with something or has a leak. I use a hand vacuum pump to test operation of the switch, diaphragm and look for leaks.