Hi @Emaries, welcome to the Sonos Community.

I haven’t seen anyone else with an issue like this recently. The ways for Sonos to increase volume is via the Sonos App, the volume buttons on the Sonos Arc, your TV remote, or via the TV connected to the Arc. Without looking into the system, I can’t say what is causing the issue you’re experiencing. 

I’d suggest submitting a diagnostics when it happens again and reaching out to our support team for further assistance. They can check the diagnostics to see where the command to raise the volume came from.

I hope this helps!