One big thing to remember about using groups…not DCA’s…
On any audio group that you assign to the main mix LR output you need to unassign all the individual channels that are assigned to that group from the LR main mix output.
There is a ever so slight amount latency processing difference between sending a channel directly to the main LR mix and sending a channel through a group and then sending that group to the main LR mix. When the two sources combine at slightly different times you will get some phase cancellation. Try it and you’ll hear what I’m talking about.
Someplace there is a note about that in the manual.
If you are using the group for other purposes and not assigning them to the main LR mix
there is no need to unassign the channels.
Other boards do that same thing and there are some higher end boards that have routing latency compensation.
On analog boards your could double assign with no issues.