How does this strike you?
This is the online manual for my new light.
I was out riding this am early and my light started flopping around as I hit bumps.
Came home and started investigating and found the following. Loctite says not to use it on plastic - the screw is metal and the receptacle for the screw is plastic.
By the way - it is a bit challenging taking things apart and tightening a screw in pitch black, with only the light for light!
Sigh - and I just ordered another one!!