..."Slight" movement of the washer behind the lock nut means one has to put some ass into the screwdriver to move it, and not being able to flick it with your fingernail, so to speak.
I agree with Paul. When installing the race, one has to be precise.
My method is thorough cleaning and inspecting the hub for cracks and what not. After removing the race, with a tapered brass drift with a substantial lip (land) with a smaller outer diameter cut just undersize of the outer diameter of the race.
I thoroughly check the intermating surfaces for burrs, and remove them if I find them.
Here's the fun part. While all of the cleaning and checking was going on, I placed the race in the freezer, a few hours earlier. When it comes time, after finishing the prep, I heat the hub with a propane torch evenly, while constantly keeping the torch moving, slowly, until it is too warm to touch, approx 140-150 degrees F.
I then place the race, square with the hub, and push it into position with a gloved hand and fingers, quickly. The temperature differential almost sucks the race into place. I follow that with the brass drift and ensure it's all-the-way home and square.
One can see from the backside if the race isn't square or all the way home.
One also has to consider, burnelling, or cold worked races, from long periods of vehicle storage, with the weight on the wheels. Bearing races of tapered rollers have been found to have some level of cold working from being stored on a shelf over a long period of time. Sounds like a "wives' tale," I know, but it's true.
Our front bearings are tapered rollers, and full engagement is required; however, to over-tighten them will cause cage failure, and the worst is ceasure and spindle failure. Bearings are cheap.....take the time to make it a good installation. They work just as hard as the bearings in your engine, if not more, because they see enormous side loads.
...that was my 3 cents worth...hope it helps...oh, yeah...use a good grease, not the cheap stuff....and properly feed the bearing by hand.
Dave