Wow that’s a pain. Where are you connecting from to get to your sjc app? You can see this at https://debug.fly.dev
This could just be some weird interaction between our proxy and your app. You can test this by connecting to your app over 6PN and testing upload speed. You’ll need to make sure your app listens on :: (instead of 0.0.0.0) to be available over the private network.
Once you have that listening, you can create a wireguard connection with fly wg create, connect, and then do something like this to hit your app:
curl "http://[<private ip>]:8080/path/to/url"
You can get the private IP with fly ips private. Also, make sure the URL includes the port your app is listening on.