Quick update on this bug for Cubase 12 (pc/win 11):
This still seems to happen. It’s a very rare case and it only happens when an output bus is rerouted with alt-shift-click on a multiple track selection. You shouldn’t do that anyway, but also the routing change shouldn’t apply to tracks that can’t have an output routing. Sometimes it’s quicker to just select everything and reroute, in this case some sanity check seems to fail, if a track is included in the selection which shouldn’t be changed.