RekordBox and XDJ-1000MK2 - Link bufferring

what brand/type of network switch are you using as a hub for the xdjs/rekordbox? is the hub connected to any other device/router/switch/etc besides your PC and two xdj-1000mk2?  sounds like you've covered all your bases so my first guess is that :

idea #1: your switch is mucking things up. super simple unmanaged hubs seem to work the best, particularly when used as dedicated rekordbox/dj hubs (ie. not connected to your larger home network and/or the internet).

idea #2: try turning off your PC/Mac wifi, allowing rekordbox to LINK with Pro Link network solely via a wired (ethernet) connection. "

idea #2.5: just for fun, if you have the cat5e LAN cables that came with the xdjs, try those and/or any cat5 cables. 

idea #3: if you were using a DJM mixer with Pro Link capabilities, i'd suggest making sure the xdj player number matches the mixer's channel number. i don't think it matters as much with a non-pro link mixer, but try setting each player number manually; and make sure that both players have 'on air' turned on.

idea #4: download and install the PRO DJ LINK BRIDGE - the xdj-1000mk2 isn't listed officially as a compatible 'BRIDGE' device, but they show up on the Link Bridge utility none-the-less. if there's a Pro Link network issue happening, the utility will usually see it:  https://www.pioneerdj.com/en/product/software/pro-dj-link-bridge/software/overview/

let us know how things turn out. m+

Tried a few brands, from Cisco to Netgear. Even tried direct link between the XDJ and the PC or Mac via wired (wireless is always disabled) using multiple cables.

Will try to narrow a few more things and follow your suggestions and report back.

The best troubleshooting option is the direct connection; one XDJ direct to the computer. Ensure that your firewalls are disabled, that you have no unique manual network configuration, and that all other network and file sharing services are disabled.

Because the PC had dual nic's, I have setup with another simple switch the two XDJ-1000MK2 and the PC and things are starting to improve.

I can play FLAC via Link however one of the players has random emergency loops (even if playing the same songs) Replaced network cable and swapped cables between working XDJ and no-working one. Is there a possibility that one of the players has an issue ? Also even trying to get out of emergency loop, the exit button cannot be used (frozen) for a few good seconds.