Disc brake dragging

I just replaced hydraulic disc brake pads. My previous pads were dragging slightly, causing resistance on the front wheel.

I got new pads, cleaned the calipers, made sure the pistons were properly cleaned, seated the caliper properly so there was no drag when I free spun the wheel. Everything was great. Took it out for a 5 mile test ride. Everything was fine. The front wheel still spun freely with no drag on the brakes.

The alignment procedure I used was to loosen that caliper, clamp down on the brakes hard, then tighten the caliper bolts while the brake was engaged.

I rode the bike to work today and the drag is back. I spin the front wheel and it stops pretty quick because one of the pads is dragging on the rotor.

Rotor is true. It's a steady drag, not just on half of each rotation.

I thought all this was fixed when I cleaned everything and put in new pads. I really thought it was fixed after 5 miles when it all worked well. But this morning's additional 3 miles and the same problem I had with the old (very worn out) pads is back.

I'm out of guesses and things to check.

Any ideas?