Is this normal on test print AND clean drop-detectors

Hi,

Although my diagnostic images are coming out perfect in colour, I printed anoth test from the printers admin area (menu-->press down+cancel) and got these results:




NOTE: the yellow. As the shade of yellow changes it goes wierd. If you look very closely the yellow is there - but its an odd c olour. A magenta or something. Does this look normal? Sure between all the shades it should be white like the rest???????

Also -- a member of staff here last weekend informed me there was a paper jam and when it restarted and went through the (lengthy) 1-4 steps on loading between every step and notification came up:

"52:01. Clean printer drop-detector"

What does this mean? And how do I clean the drop-detector?

Any advice or comments would be great?