Originally Posted by Andrew R Stewart

So here's a possible explanation. When out of the bike the hub bearings are slightly preloaded outwardly. So the inner races are a touch wider apart then the outer races are. The QR compression does it's thing and the inner races are squeezed closer to an alignment/preload point of neutral load. So the slight looseness is actually how the bearing sits naturally, as others have already said this is the way of radial contact cartridge bearings. Andy.