Get rid of the rear compensators, and just run a fixed pressure to the rears via a bias valve. Then that will eliminate the question of faulty compensators.
Defiantly check the calipers, could well have one that is sticky. Worth checking as you don’t want to take chances when the breaks are involved.
But dont be put off by the haters, if its done correctly and tackfully, the rear disk conversation on S2 works very well. Also think about the brakes at the front, it will help if you go for some bigger stuff, or imo cossie stuff as a minimum with rear disks.
Good luck mate.

Cheers