As with everyone else that appears to have vibration issues with their kickr, I replaced the bearings on the flywheel. The vibration went away for about 4 rides, then started coming back. So I took it apart again.
The first time I took it apart, I noticed iron dust in the area that is inside the flywheel. I could not figure out where it came from, but I cleaned it. When I took it apart again, this time there was more iron dust. WTH? So I took a good look and found out that the wavy spring steel washer they use to keep the axial preload had eaten into the flywheel at the flywheel/shaft interface. This was allowing the flywheel to move in/out axially about 1 mm. Now we have a spring/mass system, and depending on the forcing function (the pedaling speed) the vibration was different at different cadences. I ended up making several steel shims/washers with an ID of 11/16" and OD of .9" in thicknesses of .03", .04", and .05". The .04" one did the trick, it allows only a slight axial movement of the flywheel, and lets the spring washer keep the preload correct.
When I purchased the Kickr, i adjusted the belt tension so that it was not as high as the factory. The bearings I took out were not “worn” and were still good, they rolled smoothly even under pressure.
So If/when you decide to replace the bearings, if there is iron dust on the flywheel side, make sure to check the axial play of the flywheel. You can see the wear on the spring washer also, it will have 3 shiny spots on it.