Rekordbox > XDJ-RX2 ; Link Export will ONLY WORK WHEN WIFI IS ENABLED (with video)

EDIT - TLDR;

This issue was resolved by re-installing the OS (basic install from current OS, didn't take too long). I assume a driver conflict was creating a problem with the network.  I am now operating Catalina using the Realtek USB Ethernet adapter (can be found in XR2 download section) and so far the Link Export is working as expected via USB ethernet.  Anyone with the same issue after trying all the troubleshooting below I recommend to install the OS again (doesn't need to be a "clean install)".

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System:

Mojave 10.14.6

Macbook Pro Retina Early 2015

Issue:

Rekordbox Link export only works when initiated whilst there is an active WiFi connection on Mac.

Synopsis:

1. When WiFi is enabled and connected to internet I can click "LINK" and Link Export works and I can load tracks to any linked deck on RX2 via Mac.

2. If WiFi is disabled I will click "LINK" and the Link functionality does not work.  Library does not load onto RX2, tracks will not load to RX2 decks via mac. However I can see on RX2 display that the connection is active.

3. Furthermore - If WiFi is enabled when I click LINK, I can use decks as expected and then disable the WiFi, and the Link Export functionality continues to work as expected.

Example 1 does not apply when connected to internet via Personal Hotspot.  Only works as expected when connected to internet via WiFi.  

Example 1 does not apply when WiFi is enabled on Mac but router not connected to internet.  

Example 1 does not apply when using a public network such as a WiFi hotpsot in a venue.

Exporting tracks to USB is unaffected.

RX2 functions normally.

Troubleshooting steps taken:

Tried multiple USB cables, tried a different RX2 device, updated rx2 Firmware, mac software and USB link drivers to most recent updates. Turned firewall off. Renewed DHCP lease on USB 10/100 LAN connection. Sharing turned off. Disabled third party AV/monitoring.

I believe this could be a networking issue. Literally as soon as I turn my WiFi on and click link, the link functions correctly. I can see the message "USB 10/100 LAN has a self-assigned IP address and will not be able to connect to the Internet." Not sure if relevant but, nonetheless, I have spent a long time trying various tweaks to get the Link working with WiFi disabled. To no avail.

Worth noting there does not appear to be any other type of network bridge after installing the Realtek adapters - nothing changed.  But the fact it works when WiFi is enabled makes me think this isn't an issue.

Please see video... can anyone assist, as I need to be able to use Link Export in venues where I am unable to access WiFi. I understand that functionality of Link Export should not depend on there being active WiFi.

Link to video:

https://www.dropbox.com/s/o4ihbnwpgxvmmlj/EDFAA10D-242F-4D54-8A8A-161D0E8A9126.MOV?dl=0