Printing via Lightroom introduces banding Canon iX6850

I don't know if anyone can help, but I have recently bought a Canon iX6850 printer and am struggling to get good quality prints out of Lightroom Classic. I am experiencing banding including faint black lines, which are noticeable in the whole print but especially in the top corner of the attached example. It seems to print fine outside of Lightroom...

I have tried two different papers: Fotospeed PF Gloss 270 and Platinum Etching 285. For each one I used the relevant profile. I have done hardware tests and it is not the hardware. It prints clearly with no banding from Windows Photo viewer and the print heads and rollers are fine (I haven't used it much yet).

The colours are a long way off too, but I suspect this is because I haven't calibrated my monitor.

Any help would be appreciated!