Attention all electric brake scientists:

I've got a new situation here. TV: 2011 F250 WITH FACTORY BRAKE CONTROLLER. TRAILER: 2007 25' SAFARI SS SE. HITCH: PRO PRIDE WITH JACKS SET AT 6.75". TRAILER LOADED WITH USUAL SUMMER STUFF, FULL FRESH, EMPTY GREY AND BLACK. TRUCK LOADED WITH USUAL SUMMER STUFF. BRAKE CONTROLLER SET AT 6.5, JUST BELOW WHEEL LOCK UP. WHILE DRIVING IN HEAVY RAIN, I BRAKED TO SLOW DOWN FOR CONDITIONS AND BOTH THE NOSE OF THE TRUCK AND REAR OF THE TRAILER PITCHED TO THE RIGHT ( THE JACK KNIFE POSITION ). LATER ON, UNDER DRY CONDITIONS, THIS CONTINUED TO HAPPEN IN 90% OF BRAKE APPLICATIONS. OCCASIONALLY, IT WOULD TRACK STRAIGHT. YESTERDAY AT HOME, I WENT OUT FOR A TEST RUN TO TRY AND ISOLATE THE PROBLEM: TRUCK EMPTY, CONTROLLER SET AT 5.5, TRAILER EMPTY EXCEPT FOR FULL FRESH TANK, PRO PRIDE ADJUSTED FOR LIGHTER LOAD. AT 35 MPH, JUST A SLIGHT VEER TO RIGHT. AT 60 MPH, IT WAS BACK TO THE JACK KNIFE POSITION. AT ANY SPEED USING THE MANUAL BRAKE CONTROLLER ALONE, NO SWAY. AT ANY SPEED WITHOUT THE TRAILER, THE TRUCK TRACKED STRAIGHT WITH BRAKES APPLIED. GIVEN THE SYMPTOMS, I FIGURED I HAD POOR BRAKING ON THE RIGHT SIDE OF THE TRAILER. PULLED THE RIGHT FRONT AND RIGHT REAR DRUMS: NO GREASE EXCEPT WHERE IT WAS SUPPOSED TO BE, SHOES IN GOOD SHAPE, MAGNETS ARE 2 YEARS OLD AND IN GOOD SHAPE. DRUMS WERE TURNED WHEN MAGNETS REPLACED. WITH CONTROLLER SET TO 10, 10 VOLTS AT BOTH WHEELS, RIGHT FRONT MAGNET AT 3 AMPS, RIGHT REAR MAGNET AT 1.3 AMPS. IS THIS THE CULPRIT? I THOUGHT THAT AMPERAGE WAS PROPORTIONAL TO VOLTAGE. ANY THOUGHTS OR SUGGESTIONS WOULD BE APPRECIATED.