Brake Drum Shoes/linings problems of the 2000 Hyundai Elantra

Thumping noise in rr wheel at 104 miles - rear shoes binding on backing plates- remove and resurrface both rear shoes and backing plates. Again at 1587 miles rear shoes binding on backing plates - again r/r both shoes and lube backing plates. ~9000 miles thumping again, service could not hear. At 10,251 miles returned with same thumping complaint - service determined rear drums out of round, replaced rear drums. Thumping noise returns at 42,450 miles, resurfaced front brake rotors & resurfaced rear brake drums, cleaned and adjusted rear brakes. Shoes and pads all still fine with plenty of life left.