99 Cadillac Escalade Rear Brakes Lock

I have a 99 Cadillac Escalade with 96K mi I replaced the rear brake shoes and right side wheel cylinder. Everything was working for a few hundred miles when I noticed after the vehicle sat over night when I lightly applied the brakes while exiting my drive the rear brakes would lock. They would unlock when the peddle was released and after a couple of stops the brakes felt fine until the next morning. The shoes have a beveled leading edge and the master cylinder has been replaced since this occurrence. Any thoughts would be appreciated.