Another thing to check out when working on your trailer brakes. Check the magnet wire and brake actuator arm interference.
At one time I had pulsating brakes upon application. When I removed one of the brake drums I found that upon application of the brakes the brake wire shorted against the actuator arm. This short released the brakes upon which they applied again, then shorted out etc. This was from a factory new condition, before the brakes had ever been opened up!
Now when I work on the brakes I make sure that there is enough clearance between those two items.
2005 Dodge, 2500, auto, 2wd. Pac brake PRXB. CB, Max Brake Brake Controller, Rhino Lining, Aero 60 gal. replacement tank.
1998 Hitchhiker ll, mod#31RLBGBW, RBW L'tl Rocker Hitch, Generac NP50 G generator