Advice on rear wheel sticking

I have been restoring my 1973 series 3 for a couple of years. I had removed the brakes and replaced all components. I first thought the brake drums were sticking because after sitting for a few days the rear wheel would lock up. I checked the new brakes and even drove for quite a bit ensuring i was bedding the brakes in but the wheel continues to freeze when it sits for a while. I left it with a local mechanic who told me he fixed it but it still ceases after sitting. when i go to move off it will go forward but in reverse it totally ceases.any advice would be greatly appreciated