It's also possible there are​ brake hardware problem. The tiny areas where the brake shoes rest on the backing plate should have a small amount of high-temp grease (don't want any on the friction material itself or the drum). And the return springs can lose some strength, especially if the brakes have overheated, and fail to pull the brake shoes away from the drums.. There are also other links that can get sticky and cause problems. Most of these things don't occur but when you're looking for a reason for dragging brake shoes, it's another possibility.

Chip Bearden