That’s not a problem of obs. That are the restrictions of facebook. I assume that is because of streaming music. The crawlers recognizes you are playing copyright protected music and usually between 35 minutes and more the stream is cut off.
Exactly. The Facebook UI has been updated to tell you exactly what's happening, at least the desktop version does. I have to talk throughout my workout to throw off the algorithm. If I had to guess, it takes the algorithm about 30 seconds of hearing the raw audio for it to throw a flag.