Looks rather cool up there. What is the humidity in your shop? It sounds like you may have a static problem where the wheel tracks are either attracting or repelling the ink. there is a ground strap under the cover that goes from the frame to the pinch wheel lever that will help (somewhat) overcome this by grounding the pinch wheel system and allow you to use more pinch wheels.
Alternately, you can try turning down the print and preheat to reduce the expansion of the banner material as it goes into the printer. Also, along this line is to make sure that your banner material is already up to a comfortable room temperature before printing - as opposed to bringing it from a colder storage area or right off the delivery truck.
Finally, I would attach the banner material to the take-up reel before starting to print. This gives you the best chance of making sure that it is aligned properly. Likewise, make sure that the media is loaded in straight and that the supply roll is not telescoped out at all.
