Same symptoms appeared on mine a few years ago. The leaking brake fluid had dissolved the glue holding the brake lining to the shoe and the lining was moving loose inside the brake , sometimes catching and blocking the wheel rotation.
Use a very good and large size phillips bit to unscrew the two screws. Remember the screws do not hold the drum in place: they are there as a tool to help pulling the drum off as Peabody says. . I had to use heat almost every time to get them loose. Now I keep them in a safe place separated from the drum to avoid that problem when I need them to pull the drum. IN fact, if you happened to have other screws with the EXACT same thread, you do not need to fuss around removing the original: just use yours to help pull the drum off.