Printhead collides with print after manual colour change
I'm trying to print a black QR code on a white background using my MK3S+. I'm using white and black PLA and setting a manual colour change using Prusa Slicer. However, after completing the colour change, the printhead returns to the incorrect layer height causing it to melt holes into the print before pausing due to a detected collision.
I've recently upgraded to the latest firmware and am using PrusaSlicer 2.7.0. The peculiar thing is when I scale down the print (from 18x18mm to 6x6mm) the colour change is successful. I've also tried colour changes on a small stringing test at different layer heights which were all successful. However, as soon as I increase the scale of my QR code it returns to the same failure. I've searched around for answers but haven't found any and was hoping if someone more knowledgeable might have an idea or could point me in the direction of a possible fix.
Much Appreciated.
RE: Printhead collides with print after manual colour change
EDIT: I mis-typed, the original size that failed was 18x18CM and when scaled down to 6x6CM it printed successfully.