HP LaserJet 500 ColorMFP M570dn printing magenta streaks

[LodaHe]

I found my HP Laser Jet Pro 500 color printer kept printing streaks recently. When I opened the side door, I found there are magenta ink on the roller. Then I tried to use wet tissue to clean it up, then the steaks faded. However, after a few days, the ink on roller and the streaks on printings appeared again. And I found the roller is hard to clean right now. Does anyone know what is the core issue? Should I just replace the roller or any other part? 

Thanks!

[Repairatrooper]

Based on the distinct magenta coloration of the defect I would suspect that your magenta cartridge is leaking and possibly the waste toner hopper at the end of the transfer belt is clogged as well. Also note that typically wet cleaning of the secondary transfer roller is not recommended as this can impair the static charge applied to the roller to make the printing process work. This model is notorious for having issues with the transfer belt, sometimes you can pull the belt out and open the shutter on the left side of the waste bin assembly on the belt and drain the toner out. DO NOT use a standard vacuum as this will blow toner into the air where it becomes an inhalation hazard. Rather hold the belt over a garbage can, open the shutter and shake. If you initially get a fair amount of toner, that is an indication that the entire waste bin is likely backed up with toner. Also make sure that the waste toner bottle mounted next to the toner cartridges is not full of toner. Draining the waste bin does not always help as the wiper blades inside and get bent from the excess toner and waste toner will continue to be dropped back, resulting in the smears you have pictured.