I think you'll have the best luck when you glue a piece of toothpick in with Titebond or Elmer's white glue. The screw that's holding the straplock in is (usually) a wood screw, so putting the toothpick in gives it addition wood to bite into.
Loctite is intended to hold metal-to-metal threads together (e.g., nut and bolt or bolt into insert). The wood is porous relative to the kind of metal surface it was designed for, so it won't give you as much grip.
When the strap button works a little loose in the hole, the screw moves around in it's hole which enlarges it. That allows it to move around more and enlarge more, until you can't effectively tighten it.
On some instruments (old Warwicks come to mind), especially with Schaller straplocks, there's a threaded insert set into the body, and the screw is a machine bolt, so you get a really solid connection (and you can lock it down with blue Loctite). This is a nice touch that you might consider. The hole in the Schaller strap button is small (much smaller than on the Duncan-style Straplok), so the screw is narrower and more likely to loosen up. I like the Schaller system better myself, even though you're screwed if you forget your strap.
David Fung
