Many thanks for your quick reply.
Basically if sync is clicked on the left deck the beats will match up with the right deck. The right deck does not sync in the same way, however you are right in the fact that if both buttons are highlighted then sync works.
I do have a copy of DEX 3 also which I am still in the process of learning all about it. I have just tried it and yes it does do the same thing albeit on the opposite decks. Highlighting both sync buttons and all is well.
Keep up the great work.