Headphone cue issues on XDJ-XZ

When I start up the unit certain headphone cue buttons are illuminated and won't turn off.

Bizarrely, moving the slider for 'CH 3 Input' turns cue buttons for channels 3 and 1 on and off in a distinct pattern, and moving the slider for 'AUX' turns cue buttons for channels 2 and 4 on and off in a distinct pattern. If a cue button is illuminated when I move these sliders then I cannot get it off until I move the slider again.

In addition to the above, when I set 'CH 3 Input' to phono and play vinyl through that channel, the sound cuts in and out momentarily each time I the channel 3 cue button either on or off. The same happens on channel 4 but not when I hit the channel 4 cue button - it happens when I press the 'HI' button of the FX Frequency section.

Also, if I play a vinyl on channel 3 but slide 'CH 3 Input' to Line, when I press and hold the channel 1 cue button the channel 3 vinyl is auditable over the master channel.

Cannot get my head around any of this. Unit is brand new, arrived on Friday, serial number manufacture date in October 2020. Firmware updated to v1.12.

Please help!