Can you verify with wireshark that the traffic is only going through your lan? I’m not hip enough for nginx but I used to have to run apache under gdb all the time to trace random errors from the server. That would be next, if the traffic is really local.
Maybe Trump could escape the US by hiding in a box disguised as “music equipment” (https://www.bbc.com/news/business-57760993). Then the USSS wouldn’t have to accompany him.