So, to test if this is the adjusters or something else in the brakes, jack the car up and set the rear brake adjustment using the star wheels, make sure that both rear wheels are set with the same clearance. So I adjust the star wheels until the rear brakes just drag on the drums, then back them off one click on the star wheels so the drums spin free. DO NOT BACK UP before you drive. Drive the car and see if the same, single rear brake locks up when you jam on the brakes.
If the same rear brake locks up, you probably have an issue with the brake hoses. If they both lock up equally then the issue you have with one brake locking up after you back up while turning the wheel is likely with the adjusters, and it may not be an "issue" at all, just a circumstance of one wheel adjusting while the other hasn't yet because of the distance traveled in reverse. But it could indicate something wrong with the adjusters, since they should only be adjusting with wear and if you just set them correctly they shouldn't be adjusting all the time.
If both rear brakes are locking up first all the time, you need to consider changing the size of your wheel cylinders. That's not uncommon at all, especially if you're not running the same size wheels and tires on all 4 corners.