That doesn't look like typical banding to me, what does your nozzle / test print look like?
The first thing I would look at is the linear encoder strip and try cleaning it with a very soft cloth and either water or isopropyl. See if this changes the problem at all. Normally if it was a bad / dirty encoder strip on my old SP540 the most obvious sign was a shift in printing however on occasion it did affect colour and print quality.
If cleaning doesn't work, you should consider either replacing or flipping the encoder strip around.
It could also be ink starvation, and you may need to replace the cap tops and dampers, be careful doing this as according to my technician on occasion this can cause a crack in the print head.