I've replaced the brake shoes, cylinders,
hose and master cylinder.

man, dude, why did you sink so much money into a simple problem? the ebrake lever is out of adjustment. go through it again and make sure they're adjusted correctly

has leaking grease seal for rear end leaking causing brakes to grab your fist answer is completely wrong

l Have them both beat ! 26 years as a GM Corvette Tech LOL But l would agree with ur second reply .Probably a Axel seal . Look at ur drums & see if one is coated in oil where it meets the backing plate .If it is then ur shoe is coated in 90 wt oil & should be replaced .It is really not worth cleaning it . Pretty common.How ever if u have replaced the shoes & there r no oil leaks u probably have one adjusted tighter then the other one .Back off the adjuster of the one that is locking up .Most have a little slot on the backing plate so u do not have to remove the wheel. Sometimes the adjusters will freeze up so u need to make sure they r free . They r self adjusting But if one freezes up it could cause ur problem