70 Road runner, stock 11" drums. Front left continually adjusts looser over time, and fairly quickly. I set it so there is enough drag to get about a turn when I spin the tire, and w/in 20-30 miles it's loose again. More than about 100 miles and it's dangerous, that side is so loose that when I hit the brakes it pulls sharply to the right. Adjust it out and everything is ok.

I just had it apart, and confirmed it is a left hand adjuster. I double checked that everything is connected correctly, and took a pry bar and moved the rear shoe back at the top, and it did click the adjustor. I double checked that it is going in the right direction, i.e. when the adjuster is turned, it is expanding and not contracting.

Had a mopar friend take a look, and he saw nothing wrong either.

What could be causing this?