Whenever I turned a set of drums I always arced the shoes to fit.
Making sure that the drums were still in specs.
Sounds like its heat related.
what is the Condition of the springs and are they attached correctly and in correct positions?
Drum brakes work by locking in position when pedal is depresses and then they have to unlock when released.
Have you tried loosening the adjustment to see if that works, if so you can eliminate the hydraulics.