[Horace Williams]

Here’s a workaround:

Press cntrl/alt/6 to access the mixer window. You can then adjust your master levels (or anything else in the master section) without the mouse freezing and continue with your work uninterrupted. Everything functions perfectly from the Mixer window.

Shame on Sony for not correcting this. It’s been almost two years since your post. I just upgraded to 13 and found this workaround through sheer hacking and trial and error. I first encountered it when trying to re-assign my main outputs from the master section on the main timeline. Not how a professional in the industry should be spending his time.