That is some serious B.S. right there. I guess they are covered under 2 different warranties, so I don’t know how that plays IRL, but man.
It sort of makes sense. Replacing the drive unit requires doing a firmware update/redeploy. If your MCU isn't working they can't do that. And you can't expect them to replace the MCU for free when it is out of warranty just because something else in warranty failed.