Just tested once more: fading ok, start and stop too (besides I stop at a 'bad' time...see the screenshot).
(I have watched a large latency before start and while moving the volume fader but I think its caused by this rudimentary test program!?)
But the click while stop is normal I think....if I don't stop at the zero-crossing I ever get a glitch/click. Thats also the problem if I stop cues 'hard' or use the "esc" key to stop all audio.
It causes almost always a huge click at the PA. Would be a nice feature in SCS (or the bass mixer audio driver) to do always in that case a very fast fade out to avoid this clicks!?

But....yes......using Bass Mixer: no clicks when starting playbacks!
Maybe there is some buffer not empty...I dont know....but hope this infos could help to find a cause an solve the problem with our RME card!!?

Greetings
Christian