Brakes getting hot after rear brake overhaul

[jrusher]

Did some searching came up with a few checks to make but wandering what else I could be missing

1965 c10 original 4 drum set up single pot resi, had a rear wheel cylinder let go so I installed new shoes, brake hardware and new wheel cylinders on back, drums looked okay but didnt measure need to get a bigger mic or caliper to confirm I.D. Also replaced one section of line to the right rear cylinder.. Didnt do fronts as im swapping in discs in a couple weeks.
Set adjusters till i got slight drag, one side is adjusted out quite abit , bleed all cylinders down many times, e brake is also unhooked.
After driving a short while the brake pedal goes rock hard and the brakes slowly lock up and get hot, the rear ones only
- so i bleed them down again got some air outa front and same thing after driving awhile pedal goes hard and rear locks up
- so i pulled drums and slowly pumped brakes to see if the cylinders will extend out an retract and they wouldnt retract so air lock maybe? I cant see any damaged or bad lines brakes worked perfect before .So i bleed all 4 cyl again round and round , brakes work perfect on jack stands then same thing after driving for 10-15 min stop and go they slowly lock up ? This time all 4 wheels are locking up and getting hot.
- not sure what to try next ? I dont think theres air in system as ive bleed them many times ? Fluid doesnt seem to returning to resi maybe a bad line up front or the section going to the back T at diff ? Maybe the one rear drum is oversized so much that the wheel cylinder is over extended and wont retract? Its just weird that i never had issues before i changed out the rear shoes, cylinders etc. Ive never had issues before when putting new cylinders on and overhauling brakes, change parts and bleed them down and go