Never seen this before - Parking Brake Shoe Replacement Help

[Doubeleive]

how does the cable look? it should be attached to the panhard bar, I haven't ever heard of anything like this so maybe double check that you have the parking brake pad installed properly and compare each side and inspect both sides carefully inside and out.
doesn't make sense though if the adjustment is all the way in

 

[Doubeleive]

I don't know the GMT900 chassis as well as my GMT800, but if it's anything like mine the parking brake cables come in four pieces. The intermediate cable may (should?) have an adjuster and an equalizer where the two rear cables connect:

View attachment 440457

One or both of the rear cables could be stretched or broken, too, which would cause issues engaging the parking brake. The whole mechanism where it goes through the backing plate should be carefully inspection for correct operation. I'm curious as to what you'll find.

are the parking brake pads left/right designed? like standard brakes? I have only done mine once or twice and I don't recall, I assume there are identical though