73 Duster front disc brakes dragging when hot

I've tried searching the forum for appropriate solutions but not having much luck so here goes:

1973 Duster with new master cylinder and booster, brake lines recently bled.
Front discs work fine when cold but start to drag when the brakes (get hot).
I can feel in the pedal that there is no play.

I took her out, got the brakes warm enough that I could feel it starting to drag, then quickly jacked up the front and felt that there was definitely resistance on both wheels. I could still turn each wheel by hand but it was not easy.

Ideas?

Thanks in advance for any tips/thoughts!