[wingnut60]

Unfortunately, the self-adjusters only adjust when applied backing up--which doesn't happen often enough with a trailer--and they won't keep tightened. They have to be adjusted by hand. I had them done on the '05 and it made a huge difference. The mech said there was plenty of lining left, but they were new axles/brakes 2 years back at the time.
If you are getting a bit of a drag using the manual lever, then the brakes are working, just not adjusted, or worn out. After all the years of use, might be time to have a mech pull them all, clean everything, check magnet condition/shape, drum for gouging, and adjust. I am at the point in my life that I no longer enjoy doing that type of work, so I have it done.
Over 10 seasons of use, the electric brakes on the '05 were a constant source of concern, and I lost complete use of them several times until I completely rewired the junction box in the pin box. That might be your first check--are all the wire nuts tight and sending power to the brakes?
And the Ford IBC was always "working" according to the Ford techs that looked at it--remembering that they are auto mechs, not trailer brake techs...
Joe