could it be possible the calipers are binding on the slides or pins when heating up ? know you have said opening the bleeders releases the offending caliper[s], but could they be cocking on the mounts slightly during application, then not releasing fully, building up heat, then getting worse every brake application ? just throwing something out there, trying to help. i have been told i'm full'a $heet before, so this may be another of these times............
