[SaschaP]

I'm bringing this thread back to share my recent experience with this issue and to hopefully to shed some light on a (sort of) fix that works for me ...

My current system:
Mac Pro 5,1 12 core
64GB ram
OSX 10.12.1
Pro Tools 12.7.0
HD Native PCIe w/ Avid Omni

I've been using this same HD Native PCIe / Avid Omni combination for several years across 3 different Mac Pro's and from PT version 9 up through my current 12.7 set up.

I have always had -9171 and -9172 "Audio processing could not complete due to conflicts with other CPU tasks or a potential clocking issue..." errors to some degree or another on all my HD Native systems. The CPU usage would never be more than 50%, sometimes as low as 20% with a low track and plug-in count and no matter what the errors would pop up from time to time.

Over the last two weeks I've switched my playback engine to the Mac Pro's built in Digital output and voilà! no more errors. Not one. I've been running 60+ track sessions with HEAVY plugin usage and a playback buffer of 64 with zero errors. The CPU usage generally sits around 25% unless I go nuts with plugins. The min I switch back to HD Native the same session will double in CPU usage and the errors start up unless I raise the playback buffer significantly.

I suppose my particular card my just be bad, but given the amount of posts on this issue I'm pretty convinced the errors are due to poor communication or a bad driver between PT and the HD Native card in general.

I highly recommend you give your computers internal audio output a try and see if the errors stop. It's not a real solution but might it be a workaround for some.