Maybe I’m being a bit too paranoid here, but after assembling all my wheels, I noticed that the shim in one of them slides all over the place inside the wheel (between the two bearings) when I shake the wheel. I tried shimmying the shim to center it and pressing the bearings down, but that doesn’t seem to change anything. Is this something I should be worried about? My best guess here is that this particular V-Wheel just has a plastic notch that’s a tiny bit taller than the height of the shim.
From my experience, the sliding shim is not a problem. Furthermore, a sliding one is better than a firmly pressed one. I had both during my DIY. The firmly pressed one made noise and was stuck some time when testing V-wheel.