Audio Volume Levels Change When Playing YouTube Video or Opening Games

Scenario:

Step 1: I am watching a video on YouTube, in the Firefox browser, at volume 50.

Step 2: Close browser and turn volume down to 20 (or mute).

Step 3: Re-open browser and navigate to YouTube. The browser is still 20 (or muted).

Step 4: Click on any video to play it. When the video opens, the volume automatically jumps back up to 50 (and unmutes).

Conclusion:

I've tried this several times and it seems that the volume adjustment is tied to the last volume value I used when watching a video in YouTube, after the browser was closed. So if I am watching a video at volume 80, then repeat steps 2-4, then it'll jump back up to 80.

Troubleshooting I've completed:

1. In the Sound menu, under the Playback tab, I've disabled all of the playback devices, except the one I'm using. (Headphones - 2 - Logi Z407 - Default Device)
2. In the Sound menu, under the Communications tab, I've selected the "Do Nothing" radio button, under "When Windows detects communication activity."
3. When navigating to the Properties of the Playback device, under the Enhancements tab, I selected "Disable all enhancements."
4. When navigating to the Properties of the Playback device, under the Advanced tab, I unchecked "Allow applications to take exclusive control of this device."
5. I navigated to General settings, in the Firefox browser, and unchecked "Use hardware acceleration when available."
6. I checked to see if the audio drivers were updated. It says I have the latest.