Alignment Issues with c3765DNF

A few days ago, my printer started having alignment issues when printing colour with black.

I've followed the steps outlined in user guide and through the Dell support pages, but thus far, made no progress at all. I'd initually tried to adjust the colour registration, and from there the issue has simply snowballed. It is almost as though when printing colour with black, either the colour of the black moves itself out of alignment. Printing in black and white works perfectly, however.

Attached are photos to highlight the differences. The map of Venezuela (left) was printed a couple of days before the map (right). I've attempted to print from different devices - to establish if there was a driver fault - but to no avail. The firmware on the printer is current - the printer itself was a replacement from Dell after an issue with my normally-fantastic c2665DNF two summers ago.

There may be a simple solution that I'm missing, but as yet, I can't seem to solve the issue.

Thanks in advance.