SOLVED : I had same exact problem.. except static was also outputting to comteks and blew up studio village...
I temporarily fixed by resetting 633 - (turning off device and holding down menu button for 7seconds).
Firmware update 4.51 fixes this bug.
If your running versoin 4.50, and using mix assist, you are at risk of randomly outputting loud static noise across all of your output channels.
This has been confirmed by sound devices support. While using firmware 4.50, it is safe to run Dungan Automix as an alternative.
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