Hello JP42227,
The issue could be caused by the hardware or the toner cartridges in the printer. In this situation I would suggest starting with reseating the toner cartridges and gently shaking them to make sure the toner is evenly distributed. After that, you can try cleaning the fixing assembly and the ITB using the steps in the link HERE. If that does not resolve the issue, you can also try a gradation adjustment from the operation panel on the printer.
