Brakes or axle locking on 400 occasionally?

I've taken our 2019 400 on around 2,500-3,000 miles of towing and camping this year, and two times (both near my house, oddly enough) the passenger side brake (?) doesn't release. This happens after I bring the trailer to a stop. The trailer sort of hops/squeals and obviously isn't happy. Luckily it was only for a few dozen feet in my neighborhood.

Here's the odd part - once I back up a little bit, then continue forward, the issue has so far resolved. Makes me thing it's a brake issue but I'm not sure. Note that the wheel locked even when I hopped out and disconnected the brake cord, but after backing it up just a few feet it would roll as normal again.

Wheels/hubs are warm but we live at the bottom of a very steep hill so brake heat is expected. Breakaway cable is intact.

Any ideas on what's going on?