Recently I've been having issues connecting to a friend's server. Each time I connect, I get booted after 30secs with the error message “Internal Exception java.net.SocketException: Connection reset”. We're on vanilla 1.20.4 and prior to yesterday, I've never had any issues connecting to the server. Below is a list of what I've tried to fix the problem (as gathered by multiple other posts trying to diagnose the issue), all of which haven't provided any permanent solution.

1. Changed DNS to 8.8.8.8 and 8.8.4.4 - no change
2. Used a VPN (ProtonVPN) to connect to a location closer to the server - allowed me to connect for about ~2mins, inevitably returning the same error
3. Reduced my render distance to 8 chunks - no change
4. Used the commands "ipconfig/release", "ipconfig/flushdns", and "ipconfig/renew" - no change
5. Uninstalled Hamachi - no change
6. Used the commands "netsh interface tcp show global", "netsh interface tcp set global rss=enabled", "netsh interface tcp set global autotuninglevel=normal" - no change
7. Updated to and reinstalled the latest version of Java (17.0.10) - no change
8. Restarted my PC - no change
9. Restarted my modem - no change
10. Using different launchers (default, technic, and curseforge) - no change
11. Made sure OpenJDK was accepted through Windows Firewall - no change
12. Restarted the server - allows me to connect, but with extremely high latency that makes it almost impossible to play

I've tried connecting to other minecraft servers and other online games, both of which have had 0 connection/latency problems, which as far as I'm aware, confirms this is an isolated issue with the server. If anyone could provide some kind of explanation as to why this might be happening and/or recommend anything else I can try to fix it, that'd be amazing.