IPv6 and Matchmaking / 3 People lobbies
I got the chance to test Matchmaking, stable connection (lagging/latency) with a couple of people
using only IPv6, IPv6 and IPv4 addresses (DualStack) and only using IPv4 addresses.
If you don't know what IP address your provider gave you, check here: https://whatismyipaddress.com/ds-check
At least in germany a lot of providers only give out IPv6 addresses these days. That seems to be the culprit here in DBD.
If you don't have a DualStack, which means provider gave you an IPv4 and an IPv6 your connection to DBD Players could be not so stable, jumping pings etc.
If you don't have DualStack, maybe call your provider and ask them to activate it for you. Should be free of charge.
Also I'm not sure if IPv6 and IPv4 handling is a part in DBD that needs to get optimized to handle IPv6 better.
If you have the chance and can get a IPv4 from your provider, that would be the best. But as these days IPv4 is very rare, chances are not that good.