I wrote a bit on confilicts
HERE a while ago.
The answer is: it could be anything lol .... somewhere in between you and af there is a problem. It could be that you use rival providers who downgrade each others traffic.... or that you are in rival countries that downgrade each other's traffic,... or just that somewhere in between you and af there is a shitty server somewhere (could be anywhere), it could even be because you are too close to each other and the route is getting held up in some internal routing tangle. It's virtually impossible to know.
The only solution remains to somehow force the route between the two players to change. Proxies / VPNs / different ISPs / use your phone to connect .... all these things will change the route. As to whether or not you end up with better results, only trial and error will show.