had an issue last year with machine not moving. Found broken power wire going into solenoid bank for trans. machine worked fine for a couple storms. Now all of a sudden it moves here and there. meaning goes into gear when you release parking brake. and sometimes it won't. Also when plowing, it will just stop moving. Let it sit and it moves again. Second new issue its having is when you shift between gears, it won't move and feels like brakes are applied. Shift into neutral and back into F or R and it will go in whichever gear you choose. You just can no longer shift on the fly or else it comes to a stop
I have had experience with the wiring harnesses getting impregnated with oil which softens the insulation and allows shorting between wires where there are wrapped tight in the loom. I would look for places that got oil soaked or are worn through usually under the cab. The only fix we had when I worked for the dealer was to change the harness. The larger machines had a jump harness that went from the frame to the transmission. That was usually where the problem was. I haven't had to troubleshoot a WA350 so you could also have a problem in the shifter or wiring on the console under the steering wheel. I'd check the harness first though.