1124 is not a possible IO buffer size I assume you mean 1024?
What interface are you using?
What disk make/model/spec are your audio sessions and video on? Yes I know you are using disk cache. Yes I know it ran before. Make sure you are not unintendedly running a backup session off of a USB stick or network share.
Make sure you have tried everything here
http://avid.force.com/pkb/articles/e...ve-errors-9071
Especially start with trashing prefs, trying moving all plugins out of the plugin folder. Testing playback with built-in output.
you mean 1024? (yes of course)
Avid HD I/0 8X16- this was originally an 8x8 and upgraded by installing Avid expansion card-
Avid HD Sync
Blackmagic mini generator for frame edge alignment (system is referenced)
Not running the session from a USB stick. Session is running form USB 3 drive (and I also tried it from a Firewire 800 LaCie drive same result), and video playing from internal SSD and NOT the systems drive
Plugins I have are all up to date, mostly avid, but I do have CEDAR, Altiverb, Nugen, Spanner, and most high end plugins.
I am on Sierra and not High Sierra. I can not run Mojave as my computer does not have the metal card so I am waiting for apple to release the new mac pro if ever.
Still problems I would do a full clean High Sierra (not an in-situ upgrade) install or better get the needed upgrades to run Mojave and go a full clean install of that onto a spare partition or test disk and test with that with a bare minimal Pro Tools install.