[Sonny Keyes]

I was getting problems like this in PT12 for a while. But then it went further to a problem where every time I Bounced a mix it would create a state where all tracks played back through the main output at full level regardless of muting or routing.

I have reverted to PT11 so I can still function, but like you, I also have a new Mac Pro and a clean Yosemite system that never had PT10 on it. I thought maybe it was a hardware problem, but I find it interesting to read that someone else with a new system is having similar issues with PT12 and Yosemite.