i tried the new BETA but i have the same issue like in Version 5.8.1 or 5.8.2...
i use windows 10 in the latest version.
5.8.3 Link Mode is working but the loading delay is still there. i even can't say that it is now a bit faster or something... also track searching is lagging... if I sum up, i would say identical behavior.
i am sorry :(
BTW: @Frank Richter: i tried it with cdj-2000NXS player and it works, so maybe it is just a special problem with your XDJ or a local problem with your network/firewall.