I would think that the only way that little disc could break off like that is if the gimbal lock was installed by some ham fisted worker OR that the MP was somehow subjected to one heck of a jolt that caused the break.
I avoid the issue by placing a crumpled up super smooth 4x4" lint free glasses cleaning cloth inside the bubble and gently attach it. It holds the camera nice and snug without any undue pressure.
I tossed the plastic clip.