SElf Adjusting brakes, can't back up... Help!

I posted this in axles instead of here.....





Regina and I are 5 weeks into an extended Airstream trip. Prior to leaving Springfield, MO in July my nephew and I replaced the axles on our trailer with new axles and self adjusting brakes.



Everything has been fine until last week when we pulled into McKay's Bend, a BLM campground just SE of Lewiston ID. When I went to back into the spot, I thought I had lost reverse in my TV.... but it was the trailer brakes were preventing me from backing.



I drove around the campground and tried it again, no luck although I was able to move the trailer. I disconnected my plug in and was able to back up as normal.



I had thought by backing up the trailer brakes self adjusted themselves.



We left McKay's Bend and as I was pulling out of the spot, I tried backing up...it was stiff but I was able to move. I told my wife the brakes were adjusting.



When we arrived at Huckleberry Campground on the St. Joe River between Calder and Avery ID, I again found that I could not back up without the trailer brakes engaging.



The route we took north involved dang near every scenic byway in Idaho. I replaced the trailer plug in coming into Mackay ID.... other than that,,,and I am sure I got it wired correctly because my wife took a picture of the old plug and guided me installing the new one.



Any advice? Backing up the trailer brakes engage, going for forward all is ok. Disconnecting trailer umbilical cord allows the trailer to be backed.



I am at hte public library in St. Maries ID eagerly awaiting any and all suggestions!



Thanks!