MMU2S with ColorPrint: how to select which filament?  

MMU2S with ColorPrint: how to select which filament?

With the old non-S MMU2 (and third-party firmware) it was convenient to use the ColorPrint mode: I'd pick the precise layer where a color change would be appropriate (visible through a cutout for example) and use ColorPrint in MMU2 Single mode to make the printer stop for a manual filament change. When it reached this point it would move the extruder aside, unload the filament, and beep. I could then use the right/left buttons on the MMU2 to select a filament. I could press the button, it would load the filament, ask me if the color was clear, I'd pick off the extruded filament, and hit "Yes" to resume the print in the new color. It was a happy medium between the MK2's completely manual loading and unloading, and the full MMU2 purge tower plus automatic filament change. But now with the MMU2S I don't know how to make this work?

I follow the same procedure and all appears fine. At the beginning of the print I am prompted for which filament to use, the filament is loaded and the print proceeds until the color change, which moves the extruder aside and unloads the filament and beeps. So I move the MMU2S selector and tell it I'm done - and it switches back to the extruder it was using. Have I missed the correct way to change filaments mid-print?

This is in MMU2S Single mode because:

• it lets me select really specific layers rather than Z values,
• the slicing is not affected - no top/bottom surfaces are introduced at the change layer,
• no purge tower is produced, saving print real estate and (a little) filament (just for the shell on normal layers, I know), and
• I want to test the ColorPrint for when I distribute the model to people without an MMU2. 

If the answer is "well, that's supposed to work" I can go file a bug.