Hey @User123456,
Welcome to the Sonos Community and great choice for a user name
Sorry to hear though, that the TV remote and Arc Ultra do not communicate as desired. Thank you for providing the TV model, that is a good starting point. However, I’m not 100% sure, if this TV comes with a infra-red remote or Bluetooth or uses radio frequency. With the Arc Ultra connected to the TV via eArc that should in theory not matter, but the issues you describe are only known to me with IR remotes. Some manufacturers have the remote send two different signals for the same command (as in pressing volume up once = signal A for volume up, pressing second time = signal B for volume up, third time button press = signal A, etc). This is usually only relevant if using an optical connection to a soundbar, as the soundbar tends to learn only one of the two signals, hence only every second button press results in volume going up or down, mute - depending what was pressed.
Do you recall going through a remote control set-up when you installed the Arc Ultra?
Remote control aside, please check that the TV is running the newest firmware. I’d expect if this was an issue, that it got addressed since it’s release.
Lastly, I can think of it being a communication problem on the HDMI. Are there other devices connected via HDMI to your TV that could interfere? Please test the remote without any other devices connected to the TV apart from the Arc Ultra.
Hope this helps!