Setting Master Bus for Playback

I'm currently traveling with my Steam Deck, and I brought along my audio projects that I otherwise have on my laptop. I have two audio buses: 2 channel default Master Bus AND 1 channel mono bus for recording.

Problem is, whenever I open the projects, Qtractor plays through the mono bus (hard right pan) even though the channel explicitly says to play through the 2 channel stereo Master Bus. Even the mixer shows the audio going through the Master Bus via the stereo meter. So, to solve this, I have to delete the mono bus BEFORE I make the "Qtractor to sound device" connection & start playback; otherwise, deleting the mono bus after playback and connection will cause mono to stick, even if I delete the mono bus.

Did I miss something? Is there a step I should take to force or reset playback to the master bus?

0.9.31.13

Thanks!