After losing a couple of plates on my flatbed and boat trailers I now have wire backup links between the light mounting studs and the plate fasteners. I make them up out of 10-12 ga. stranded wire with crimped on 1/4" eye lugs on each end. I use 1/4" bolts with nyloc nuts at the plate. The plastic "T" shaped plate brackets fail with alarming regularity but the wire links don't yet still allow the plate to move in the wind or when scrapping the ground. They are a good "belt and suspenders" backup system. The last time I lost a plate (plastic bracket broke) the DMV kept asking me where I lost the plate!!! If I knew that I would have gone back for it.
Again, this is on open trailers but a camper could still use the same system.