Audio sounds good until I livestream, then THIS happens (sometimes)

I've been livestreaming using Facebook Live. I started off using a Focusrite Scarlett 2i2 with a phantom-powered Rode NT1-A for vocals in channel 1 ("line" setting) and plugging my acoustic guitar straight into channel 2 ("inst" setting). Gain was at 30% for vocals, about 50% for guitar.

It sounded good for the first four shows (see here and here) then it sounded terrible (see here and here). Same gear, same internet connection. Same day of the week, even (Monday).

My laptop specs: Dell Latitude 7490, Intel Core 15-8350U, 8GB RAM, Windows 10 Pro version 1809 installed March last year. The camera is, obviously, the rubbishy thing that came with the laptop. 

I've livestreamed using my phone (same WiFi) and no sound issues there, other than the quality of my phone's mic.

I'm no tech wizard - this is my first time even using some of these words - so any guidance would be much appreciated. Thanks!
Turn everything off for 2 minutes. Restart by Turning on your modem first and then your router and Computer. If your modem or router has a battery, please remove it.

Please determine if your router needs a software update. If yes, please update it. Confirm all other software is current.
It is possible your router cannot handle the streaming load or has issues handling the packets. My Linksys router randomly dropped packets so I replaced it.

Please do the above and report back. These issues are not easy to chase down so patience is needed. 
Please check all wired connections to ensure they are tight. Please turn ‘every’ device you are using off for 2 minutes and then do a restart. They could be an interface issue between your devices that I hope the restart will fix. 

Since it works using your phone, please double check the other devices.
Thanks, folks. All fixed.

I turned everything off, as suggested, then started up again but had the same issues.

I ended up reinstalling all software and updating drivers. Sound settings had the RODE mic and the laptop mic simultaneously activated during FB live streams, for reasons unknown, so I fixed that using OBS settings.