Here are my machined awning Z bracket replacements.....
They grip the drip rail tighter than a........well...let's just say really really tight.
They are milled from aluminum and I drilled and tapped 5/16" threads in them (cuz that's the kinda guy I am...) but you could just drill a through-hole and use nylocks. They are primed and painted with rattle-can black and I used some thin silicone sheet material to protect the van finish.
Each bracket required custom fitting so all three are a bit different. The objective is to get the beveled top surface to mate well with the large sheet metal bracket so that when you tighten the joint the machined inner bracket is wedged down into the gutter as it tightens on the lip.
The rear bracket was likely the last one I fabricated since it fits really well
. I also bent the larger outer brackets here and there to get the awning to sit vertical.