If you have looked at countless posts, then you've seen plenty of references to needing to check/monitor your PC's LAN usage (ie anything unexpected running) as well as your LAN and WAN traffic ... almost no one does this, and it means they are effectively driving blind. You also didn't follow the pinned post in this forum regarding posting your OBS Studio log from a problem session when asking for help
There is also a FAQ on this site for disconnects and other bandwidth issues
In general - sometimes it is your PC (things like Killer network software. security software, or simply an overloaded system)
Plenty of times the bandwidth conflict can come from other traffic on your LAN. Or using WiFi, or cellular Internet connection. IN rare cases, it is your ISP link, or ISP themselves