What you're probably experiencing is wood cell compression. Over time, under the pressure of the nut, the cell walls collapse and leave just a little space. If the space gets large enough, it can wiggle. This literally takes years to form. It happens on all the pots, switches, output jacks, and especially strap pins/locks. Just gently tighten the nut every decade or so and you'll be good to go.
On the the strap locks and pins, because of the combination of forces, especially on straplocks, you need to check these much more often. I recommend checking them once every month or two