DDJ-RR left channel fader lowers right channel fader

My DDJ-RR has suddenly developed an issue where when I lower the left fader, the right one also lowers.

I have tried different laptops, programmes (rekordbox/virtual dj etc.), resetting to factory settings and re-mapping to make sure left fader isnt set to control both.

Does anyone have any other suggestions or does this look like a hardware issue?