I hope I'm not jinxing myself
I've not had this issue with FB
Then again, I only connect to FB using Chrome in Incognito mode, log in, and I use a non-persistent stream key.
so beware standard Cookie issues on PC (or any number of other possible items that could interfere from your local PC)
I have had issues OBS PC and LAN being fine, and OBS going Red (0 bitrate) for a few seconds, for last month or so.. not sure if my ISP (AT&T fiber or FB itself)??
But logging into /Live/Producer, connecting to a Scheduled video event, copying stream key into OBS and connecting has worked fine [I can think of only one time it didn't work as expected in last year]. Now auto-start of Scheduled Video not working at all (or at least timely, whole other 'glitch' which we simply go live manually now... stupid FB.. but separate issue from OP)