Is this happening on every print or is it intermittent? At first glance it appears to be what's commonly referred to as ink starvation, although in reverse order of sorts. Ink starvation occurs during the print cycle, but manifests at some point throughout the image, not usually at the beginning. As I understand the issue it is believed to be caused by a drop in pressure within the cart during printing, so although it prints fine at the beginning it will drop nozzles during the cycle. One suggestion is to shut down the printer, pull all carts and agitate as usual, reinsert and restart the printer. If there are any issues with air bubbles or ink settling in the cart this procedure might cure it. Also, if you are using expired carts(as most of us do), this routine might go a long way toward preventing future print head issues. If you have been following my 9900 saga on Eric's thread you will no doubt have read this already in my recent post. Of course you will likely have to run some cleaning cycles as well.
Just a thought and I hope it is of some help.