way back when i had a older (70's) winnabago motorhome come into my shop with back brakes completely burnt up,even cracked one drum,someone had replaced the master cyl about 300 miles back down the road,i replaced everything on the rear brakes,took it for a drive and it wouldnt stop well just slow down no matter how hard you pushed on the petal,after some head scratching i decided it had the wrong (to small) master on it)put the correct master on it for a 400 series truck and that fixed it,however the problem started when the owner left the other shop he forgot to release the parking brake,and drove it that way for around 300 miles without knowing it
hope this helps some
a true story!!