It's the TV. You can get the same response by pressing and holding the mute button on the TV's remote. I thought there was a way to disable the shortcut in the TV's menus, but I just looked through mine and couldn't find anything. I've gotten into the habit of making sure I barely touch the mute button when I use it. I don't know if trying a different code for Samsung when setting up the remote for TV control would help, but it might be worth experimenting with if/when it really bothers you.
Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution."
If you appreciate my answer, maybe give me a Kudo.
I am not a Roku employee.