Internal Exception: java.net.SocketException: Connection Reset

When I try to join a server that isn't hosted on my machine, either I will fall through the world or just be completely lagged out (all mobs are frozen, I can't pick up items, etc.). Either way, after a minute I will be timed out and get the error message "Internal Exception: java.net.SocketException: Connection Reset." This only happens with smaller servers, servers like Hypixel being unaffected. Two of my friends suffer from the same problem, in fact, being unable to join the server I am hosting on my machine, however, another friend has no issue connecting to my server. None of us are on the same LAN. My two friends and I who all have the same issue have collectively tried a variety of fixes suggested by the internet, but none have worked. This happens both with vanilla and modded versions of the game. I know the port is forwarded correctly and this issue did not exist with my server or any other until recently. Please tell me if you need any more information than what's listed here.

Edit: This issue is not a duplicate and it is still unresolved. Can someone please reopen it?