So this seems to be the issue as far as I can tell.
The left input channels work normal with my turntables. The right side is missing one channel. So far my problem solving has included this -
Both turntable RCA's checked plugged into the mixer phono - both working in stereo.
Mixer swapped out to test for the same problem - same issue
All cables tested and swapped with new ones (incl multicore)
Needles cleaned, swapped and tested
Turntables swapped, same issue. Can rule out it is nothing to do with my decks.
Time code vinyl is brand new and clean
My desktop pc has more than enough power to run Traktor -
Ryzen 5600x / Nvidia 3080ti / 16GB Ram @ 3600mhz / Traktor installed on an M.2 drive
screen from the affected channel while running (strange it shows both coming through equal at the top)
screen from the left channel that runs fine
and a screen from audacity to show the levels coming out of the right channel. It does show a little output, but this can't be heard over the speakers.
So unless anyone else has any ideas, I feel it might be a hardware issue of my Audio 4. I've had it since 2011, however it has been looked after well like all my dj equipment.
Any advice and help would be much appreciated.
Cheers.