RESOLVED - DDJ 400 - Can hear master and cue when the crossfader is to the left

This issue has suddenly sprung up from nowhere. When the crossfader is to the left I can hear both the cue and the master output, when the crossfader is to the right the cue/master work correctly.

I have not made any hardware or software changes as far I'm aware so this is confusing. I have tried to reinstall Rekordbox, I have set the midi back to default and I have also gone into the preferances on Rekordbox and reset everything back to default but the issue still persists.

Windows 10.

EDIT: You have got to be kidding me haha. This post has just fixed it for me:

https://forums.pioneerdj.com/hc/en-us/community/posts/360056248512-DDJ-400-crossfader-not-working-to-the-left?input_string=DDJ%20400%20-%20Can%20hear%20master%20and%20cue%20when%20the%20crossfader%20is%20to%20the%20left

My decks were set up incorrectly; they were set up as 1 & 4 instead of 1 & 2. All sorted!