-metal or plastic disc? If metal, this is pretty normal as you have all these intolerant components heating and cooling, wiggling is guaranteed. If plastic discs, you should be able to crank enuf to overcome the loosening.
-put a drop of clear nail polish in the inserts before you tighten; credit: AngrySnowboarder, the BurtonAvenger.
I have had both kinds of bindings, problems, and solutions.
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