Video desyncs with the audio over time
Make sure the sample rates in both systems are the same. I don't know what OBS is, but if I was using Final Cut for video editing, I would make my project 48kHz, and make sure any external recordings were also at 48kHz. Even with the same sample rates, audio will drift over periods of more than a few minutes. Either sync it up manually in chunks, or use something like Pluralize to do it for you. (Or have a fixed sample clock  between all your devices when you record- probably not possible)