I have no idea the specifics, but using my amazing powers of mind-control:
This is on my Annual List… if you search through my never-ending F/R list.
Basically,from SB’s POV it is not a ‘bug’. What it -is- is that your routing would’ve created an invalid feedback loop. So what Cubase does is hide such possibilities.
What it -should- do is
VISUALLY indicate invalid routes (perhaps by graying out various options) or…
Allow no limits BUT give the user a nasty warning message when they try to do it.
Now… -occasionally- I’ve removed all possible offenses and even still I’m prevented… which may be a bug. But always, saving/closing/re-starting has eliminated the er, ‘issue’.
I’m sure the check is in the mail on this one.