[Matt Hepworth]

If you have different processing on your stacks of vocals that will do it. Delay compensation is *not* active on DSP plugins on record enabled/input monitored tracks. By design.

For example, if you set up two tracks to input 1 and put an AVID DSP plugin on one (10 samples) and a Plugin-Alliance plugin on the other (34 samples) you'll get crazy comb filtering.

Solution is doing just like Apollo Console or old TDM days — same plugin across each channel of phase critical sources.

The benefit of doing it this way is you could have 2.5 extra ms of latency on a guitar input (3 PA plugins), where the 3-4ms won't be noticeable, and it won't stop the vocal input with AVID channel strip from still only being 1ms latency.