Update #2:
Have about 1000km on the replacement core and mechanically, it's solid. Still as silent as on the maiden voyage. No vibrations to report.
The last two rides I did have a connection issue during the first minute of riding. The cadence and then the power would drop out for about 15 seconds leaving me stranded on the side of the road. Then it would reconnect and off I went with no further dropouts. I have many devices transmitting at the same time: Garmin Edge 500, Quarq, Garmin cadence sensor, speed sensor, the missus's Kickr and cadence sensor, so it could just be cross talk or maybe the cadence sensor could be dropping out confusing the Kickr. Who knows but it's a minor issue. Will report if the problem gets worse.
Ann's Kickr has about 900km and other than three stickers flying off the flywheel, no problems.
Overall, I'm pleased with the Kickr's we have.