I found that myself, the hard way :D Switiching from the kicker back to the rear wheel (and I've lost the spacer in the process). Anyway, Thanks for the video. At least now I know why the spacer is needed on the wheel's hub and not on the kicker's hub. 👍👍👍
The shop I bought my Tacx Neo 2 from (shimano 11s freehub) installed the cassette without the spacer, but it's not wiggling. Have not used the trainer yet. Should I reinstall? Thanks!