Poor Upstream Performance - Twitch / YouTube - Dropped Frames

Hello - have Gig+ tier home internet. Ever since yesterday evening (7/31/23), I have been unable to push a stable stream to Twitch (6000kbps) or YouTube (8000kbps). Everything was stable up until last night. Was easily able to push streams without a single dropped frame.

Now, I am lucky to have less than 50% of frames not dropped.

Xfinity Assistant claims that there's no problem with Xfinity, but I beg to differ. Nothing has changed on my end (same modem, router, hardware). Up until about 7PM (eastern time) my test stream to YouTube was solid, no dropped frames. Then 7PM hit and the dropped frames began.

How do I even begin to have this problem diagnosed and resolved?