[XJENSEN]

Well, this is my current setup:

PT Ultimate 2020.3 - Mac OS X High Sierra 10.13.6
HD Native PCIe - HD OMNI - HD I/O 8x8x8 - HD I/O Analog 16
Artist Mix - Avid Dock - EUControl 20.1.0.50
Mac Pro 5,1 (Mid 2010) 2 x 2,4 GHz Quad-Core Intel Xeon, 24 GB 1066 MHz DDR3, ATI Radeon HD 5770 1024 MB

To me, being able to use LLM and high buffers is crucial, because I don't just do tracking, but am also producing with VIs at the same time. So I tend to require higher buffer settings to keep this going.

Like you said, I also have a template with Aux sends on every channel, that route to the LLM-enabled output. I also tried routing directly to that output from the tracks being overdubbed, but that also doesn't work.

So, on my system, LLM doesn't work as advertised and as described in the manual. This has been an ongoing headache and so far I have gotten no valuable input whatsoever from Avid support. This has been going on for years. I'm stuck with a huge investment in a system that does not work.

I tried everything. Swapping the HD Native card for another one. Connecting to another laptop using the HD Native Thunderbolt box. Complete reinstall of OS. Hardware check to verify RAM is correct. Reset NVRAM. Reset SMC. Switch to different PCIe slot. Strip all other cards, like UAD accelerator. All with the same result!

The only constant for now, is the OS and the PT software. So either of those must be the cause. I'm now planning on upgrading to a Metal capable GPU and to Mojave, to rule out the OS. But somehow I have little hope this will have any effect, because I have been on a fully qualified system all this time, and it never worked.

I have once again asked Avid support to take a proper look into this, because this is really an unacceptable situation.