front passenger side fender

front passenger wheel fender has broken off where fender attaches to body of RV and basement storage units. Front bumper and front side panel still attached and does not vibrate. I removed self drilling screw and replaced with stainless steel screw w/fender washers top and bottom of fiberglass panel. Added several SS washers to relieve stress and attached with lock washer and nut. This held for 200 miles then vibration started again.

Any ideas for a permanent fix?

I was thinking big glob of epoxy in and around screw head and nut.