Brake issue

[cj847]

I have a problem I am having trouble diagnosing. I'll try to keep this short enough so that folks will read it.

1967 C10 with CPP front disk kit (installed by previous owner), new cpp booster and master cyl but the old combination valve. Meanwhile my rear drum started dripping (wheel cyl).

Long story short, I installed ALL new rear drum brakes (shoes, hardware, wheel cyl, adjusters, adjuster hdwe, drums). I also installed a new Summit PV2 disc/drum combination valve.

Everything went together and bled well (yes, I used the combination valve bleeder tool).

Went for a test drive and brakes are great. Went across town and brakes got better and better. Then I started noticing I wasn't coasting as well as normal, then the transmission started to kick down early.

THE PROBLEM
As I drive the truck, the rear drums are tightening up. It is like the self-adjusters are adjusting every time I use the brakes. (I am pretty sure they are only supposed to adjust when applied in reverse).
I took the drums back off and double checked that the adjuster and adjuster hardware are on the correct sides, and they are.
It is interesting that the drums were easy to pull off (ie as if the adjuster is NOT the problem).

Any ideas?