850K won't move flashing F

2005 Case 850K w/ enclosed cab

We pulled it in the shop, changed the filter. Afterwards it fired up for my guy but wouldn't move.
What I know/ have checked.
Parking light and gear light are always on.
It only starts with the parking levers down and I can hear the relay working when I move them so I know they work
The dash blinks F (forward) with codes 4532 & 4531
If I unplug the 6 pin joystick, then it has an always on (N) neutral with only the code 4533
The speed % gauge is always buried on 0. (doesn't move even if I try to bump it up or down)
The two power wires (19c's) show 12.5v with everything plugged in and the ground is testing good as well.
The two communication lines in the 6 pin joystick connector test 120 ohms unless I turn the key on then it drops to like -30 with everything plugged in.

I'm just a semi mechanic (don't know tons about hydraulics) but seems like a randomly failed joystick? The silly thing is we just pulled it in to change filters and such.

I read up some on the GaryHoff/Vcat post and this is where I'm at so far. Didn't know if any of this (my CASE specific) info would be a give away to any of you with more dozer knowledge.

Thanks for any help

850K won't move flashing F