I have had to replace both on my Flagstaff. Make sure you match the pre-made curve, old VS new. The 1 st. one I had to replace was due to FR installing it backwards under warranty. Replace small head screws or staples when remounting. Use hex head self tapping sheet metal screws, 5/16" head. Add an additional screw where it mounts on the outside rail-make a "triangle" w/ the 3 screws. The wire straps crack and break at this spot, this larger head gives more surface contact area and better support. After replacing these on several trailers, more than once, this been the fix. It has held for 2 years.
It you have broken several wire straps,you may need to move screws to prevent too acute an angle on straps when you put slide in or out.
PS-I have learned to carry several of the "Plastic ball and elastic strap" tarp tie down to fix these wire straps when they break on a trip. I have saved myself and others w/ one or two of these straps and zip ties.