LastAi

Try add this to your java args "-Djava.net.preferIPv4Stack=true" This worked for a member of my server.

Neat I have a user on my server that has this same issue. We tried everything and only narrowed it down to forge today. I'm going to have him give this a shot. We tried ever several different 47.x.x versions, and we able to confirm its only forge, and didn't mater the launcher of forge version.