Originally Posted by MC5C

As you suggest the things to look at now are the flex hoses and the master cylinder assembly. I would get the caliper pressured up and dragging and crack the line at the chassis end of the flex hose. If the caliper releases it's not the hose. I have zero clue on how to diagnose or fix the master cylinder, beyond double checking it's not a mechanical pedal issue not allowing the master cylinder to retract all the way.

Brian