line lock not releasing?

Do you have a booster?
What returns your pedal?

The point I am working toward is this;air is compressible.
If you have an air bubble in there, it becomes a big spring, and perhaps, without a booster, the pedal will not return to its parking spot, which will keep the compensating port closed, which will prevent the pistons from retracting, which will cause the pads to drag..............
The power booster has a big spring in it,powerful enough to return the pedal.
Just put a toe under the pedal and pull it up. If it moves, there's your problem. If it doesn't;sorry to have wasted your time. But before you put me on your ignore list, go check the master cylinder for a fountain at brake release.It better be there! Try not to get fluid all over everything.....The fluid should also roil on pedal application, as the compensating port does it's thing.