So I used some networking tools to find that Unreal Engine is, over the course of about 5 minutes, uploading ~400kb of data and downloading ~80kb of data over UDP, at which point the internet is snuffed out. I enabled Windows firewall, and set some rules to block the traffic, and that seems to have fixed the problem.
It’s still all very odd. I’ve never had an like . Usually disabling the firewall fixes issues, not the other way around. What is the traffic for, anyway? Does UE have some sort of cloud or P2P functionality that my ISP is interpreting as nefarious or something?