I ended up spending half of the day trying everything I could think of.

In the end, I was able to learn all the commands, however, the key presses (Russound remote &/or Uno2 KPs) were unpredictable.

Sometimes it would take 1 press for the cable box to recognize the press, other times it would take 8.
There were instances where repetitive press would be recognized as soon as each second; other times that same button would take 15-20 seconds.

Each time, the KP would display that the button was pressed, but the CAV would not send the command.

It seems that the buffer on the CAV was getting corrupted or ...

Any code sets that were natively in the CAV would be transmitted instantly and worked 100% of the time.

Because OEM remote passthru worked 100% of the time, I instructed client to use Comcast's OEM remote and left it at that for the moment.

I will be going back there to do some additional work and will bring URC's MX line of controllers and see if we can go that route.