19:50:40.958: Output 'adv_stream': Number of lagged frames due to rendering lag/stalls: 34 (0.0%)
19:50:40.958: Output 'adv_stream': Number of dropped frames due to insufficient bandwidth/connection stalls: 12301 (2.9%)
19:50:40.958: Video stopped, number of skipped frames due to encoding lag: 38/422218 (0.0%)
Rendering/encoding lag is below 0.1%, generally at the 'OK to ignore' levels.
Dropped frames are always a network problem. There's nothing OBS can do to fix those, it's usually something you have to take up with your ISP.
If you were streaming to Twitch, you could use R1ch's TwitchTest tool to get a speed and quality score, and go from there. Unfortunately, YouTube has decided that doing that sort of test is against their terms of service.
You could install software like Pingplotter (they have a free version) and set it to monitor the connection to the ingest server while you stream, see if it would at least suggest where the problem is happening so you get a better idea of whether the issue is in or out of your control.
Similar, you could as a troubleshooting step, try using a third-party service like Restream.io set to just stream to YouTube, and see if that re-routing could help bypass whatever bad node is occurring.
But yeah,
17:53:23.960: ==== Streaming Start ===============================================
17:53:24.335: socket_thread_windows: Increasing send buffer to ISB 131072 (buffer: 0 / 596480)
17:53:26.188: socket_thread_windows: Increasing send buffer to ISB 262144 (buffer: 0 / 596480)
17:56:06.246: socket_thread_windows: Increasing send buffer to ISB 524288 (buffer: 0 / 596480)
says that your connection is having a severe throughput stability problem. Possibly packet loss, but it just can't stably upload at the speed you've requested.
