I'm glad I saw this post. Just had this issue this past weekend. Backed the trailer up the street a ways to make room to turn into my driveway, backed up just fine. Then, went to start backing into my actual driveway (both are uphill slightly) and the damn thing wouldn't move easily. Tried it last night again to make sure it wasn't a fluke, and sure enough, the brakes go right on. I was curious the best way to trouble shoot this, so, now I know!!

I'm hopeful it's just one of those wire splice connectors, and not the solenoid.