My two cents for what it's worth.
Hard to know what the loads are vibrations or why that's loosening up, but it seems to me the real issue is that those are probably 3/ 16-in thick and there's not really enough bite. Normally you want at least one diameter's worth of decent thread engagement engagement so, if you have a you know a 3/16 in wide screw it's really marginal especially when you take stainless steel which is super strong against you know somewhat aging fiberglass. So what Parker really should have done is built in some wood stringers behind that into the fiberglass so that you're not biting into just the thin panel but rather something substantive. No you can't fault them because as someone said you know it could be a t-top which is an aftermarket and they never designed it for those loads.
My guess is that some epoxy approaches or zip ties and all those things might work very well for years depending upon what's loading that That said I usually try to improve on any situation if I can. I think there might be a couple possibilities if you can pry those panels apart enough to be able to get into the back side. I'd try to get you know one or two really decent strong connections to support the load and then the rest don't take nearly as much. Depending upon the exact situation what you don't want is for that to continue and then at some point start to crack the panels. Another pretty strong possibility would just be to find some big heavy duty aluminum or stainless steel rivets, drill it out clean but that's going to have aesthetic drawbacks, unless you can come up with a clever way to cover the front nicely