Yep, this is when the intermediate group doesn’t directly have the send or the return of the FX channel routed to/from it and the send is from a channel earlier in the chain (if the send is on a subsequent channel, it works). I think it has more or less always been like that, at least I vaguely remember running into something like this before.
You could open a bug report with Steinberg, maybe in a few years after several paid updates they’ll fix it… Or it is Cubase’s passive-aggressive way of telling you “simplify your routing”
Yeah I think I remember this as well, long time ago. But still, this is an unnecessary issue, which overcomplicates a lot of things. My workaround for now is, that I send the FX to the groups in between (here “main group”), activate them, but set them on -∞. So they always get selected as well.
But this way I have to make double the work, and it gets exponential, the more groups are in between…
Not really a solution.