You are correct. But, mch alone, works as it should. And, when switching from 2 ch to Blu-Ray mch, it works, too. Only switching from 2 ch to SACD mch requires a "Stop". So, I never thought it has something to do with my settings.
Here they are:
DSP: 7.1, no up/down mix, 192 upsample (because of 192 DACs), volume normalization, room control, channels re-order (not sure needed), Plogue Bidule VST (eq, bass mngmt, etc...)
Audio: RME HDSP (AES), ASIO, no bitstream