rear drum brakes issue

Lay a straight edge across the axle face and get an accurate as possible (depth gauge) reading to the highest point on the shoes edges. Then transfer that to the interior face of the drum. I bet the shoe edges are hitting. If that is no joy, measure from outermost edge of drum to inner drum face, then from axle face to backing plates If that is the problem, and they otherwise appear OK, it should be no problem for someone with a brake lathe to take some off the outer lip