Mimaki trying to print "white" areas

Looks like a preset setting you chose before you send the job. I have a Roland SC-500 and it is in my printers menu. I dont know about Mimakis. I will select Full Width Scan to either "enable" or "disable". This will make the cariage travel only over the printer area or ignore it and just travel the whole width of the printer at each pass. You do get lesser quality if you want it to only travel over the print area but for some jobs speed is more important than quality

 

I believe it has something to do with the file. The same thing happens to me every once in a while with my Mimaki while printing out of Illustrator CS2 to Rasterlink RIP. The printer is printing whatever is in your document space so maybe something is their that is super small or something white with a light stroke on it or something and it is printing it. Also, make sure your document size isn't set up much larger that what you actually want to print because like I said your printing the document space so it will keep printing nothing til it gets to the end of your document space.

 

It can be turned off in Flexi. I can't remember the setting off the top of my head since I'm away from the shop.
Full width scan sounds right.
Keep in mind that it will print faster but you may get banding and color shift.
Profiles are created using a full length head pass to allow proper try time etc.
When it's turned off the control factor is gone.