Did you fit new brake and retainer springs when you replaced the shoes?
I did all my brake discs, pads and parking brake a few weeks ago and fitted adjusters while I was at it. I temporarily adjusted the parking brake with the cable and every time I had a chance over the next couple of weeks I used the parking brake to bed it in. Once I was happy with everything bedded in I loosened the cable adjuster and adjusted the shoes, then re-adjusted the cable and now I have a parking brake that will hold on a 15° incline facing both directions. This was on the Serpentine on the Isle of Bute, 13 hairpin bends and a 15° climb
