Probably not your fault.
In all my years of drum brake vehicles, I only had one self adjuster setup that actually self adjusted!
That was a '67 Buick Wildcat with huge drums that never seemed to need adjusting or tweaking. My Bronco, not so much!
Chevys, Fords, Buicks, Pontiacs, finally got away from manually adjusting them often when they got disc brakes!
I take that back. I think my Toyotas worked pretty well too. I drove them a lot and don't remember ever having to mess with the brakes until they needed replacing.
The '78 Datsun brakes needed adjusting or replacing about every 10k miles. They sucked all around!
Paul