XDJ-RX freezes when loading tracks from my Macbook

Been using my XDJ-RX set very happily for a long time. I use my Macbook and a ethernet cable to load my tracks from Rekordbox to the XDJ-RX. Never a problem for all there years, until yesterday during a gig..

On the second deck (the right one) the track wouldn't load: just keeps on loading but never did... Restarting XDj-RX and Macbook and after a while okay again, but the exact same problem happened again multiple times! And always the second deck that causes the freez (with the first one to follow..). Firmare and Rekordbox (v6) up to date and had this problem never before and then 4-5 times in one set!

Anybody any idea?