everything is looking sweet and aligned. i have to undo the brake nut on the rod a little to free the wheel afterwards. ive been too scared to really hit the back brake hard for fear of bending everything. so when these little lock ups happen they are little ones. the next thing to check is the pedal end. its a bit loose up there, but honestly i cant really see how that would cause it.
Not to state the obvious...... but that spring should have no problem pulling that rod back when you release the pedal. There is a lot of tension in that spring, or should be. By loosening the nut, your making it easier for that spring to pull the rod back. Sounds like something may be binding and or bent, from that spring/ arm, through the rod to the pedal. I no longer have the stock set up, so I can't look. But is it possible that the pedal travel adjustment is sooo loose, that you are getting it into a position... down so far. That the rod winds up straight, binds and can't return?
I always adjust rear drums by putting the bike on the centerstand, and spinning the rear wheel, while slowly tightening the adjusting nut, until I feel slight resistance, then I back off just enough that the resistance is gone. I like as little play in the rear brake pedal as possible. I would check that spring, and the whole linkage for something that is binding. It may not be in the actual brake at all.