UR5U-8780L Remote oddity - Time Warner TV

This question is about "UR5U-8780L Remote oddity", with Time Warner Cable TV and apps. I am trying to help an elderly neighbor. Simple setup: Samsung TV, Yamaha soundbar (fed from TV audio out), unknown set-top box. I have it so all devices properly power on with the upper-left Power button. At that point, channel change works properly, but volume does not. Pressing the AUX button then properly addresses volume, but channel change then actually changes the Yamaha to another source input. I have not yet looked into any other methodology of device interconnection.

I have been through the remote instructions, but there is nothing I have found to nail this down to a simple power-on and the remote then knows which device it is communicating with. I am looking for suggestions for this hardware, not to replace it with a more intelligent remote.

This topic covered UR5U-8780L Remote oddity, and TWC cable tv service.