my g/f has a 99 taurus and when she goes to brake, the right rear wheel locks up and slides. I took the drums apart and didn’t see anything wrong on either side. plenty of meat on the shoes, and when the pedal is depressed you can’t turn either wheel.
It could be the adjuster ( the threads get rusted and it doesn’t adjust) You could try backing the adjust off a bit. That’ll also let u know if its rusted up. Drum brakes suck…sooooo many moving parts, springs, levers, ect.