I'd like to ask for your advice, please. I must be doing this wrong and I can't figure it out.

I have two different tail lights on my bike, a Cateye TL LD1000 and a Portland Design Works Radbot 1000. They're mounted on a kludge PVC frame, which is connected to the back of my rack. (Surly LHT, btw)



Both lights will rotate on their mounts so that they face down. The hardware stays in the right place, but the grip plates that the screw goes through jiggle loose on the ride.

I have really tightened the bolts. I have used the thread-locker stuff on the bolts. I have poured Elmer's Glue into the grip plates, and that does work for a while but then it resumes the rotation-on-vibration.

Since these lights are from two different manufacturers it must be me.
I'd really appreciate any advice.