PIXMA G620 - Black streaks on underside of print

[ashleyrod82]

I've had this printer for almost a year and it's always worked fine, but now it's suddenly leaving black streaks on the bottom of all of my prints. This is an issue as I print often on double-sided photo paper for my business. I've cleaned the bottom plate MULTIPLE times (I used about 50 sheets of cardstock) and it did appear to help a bit, but once I start printing again, the streaks still appear.

I've completed all of the cleaning - bottom plate, rollers, regular cleaning, deep cleaning and nothing has made them go away. I also turned on the "Avoid paper abrasion" setting, but it appeared to make additional smudges on my paper.

Left: First bottom plate cleaning sheet, Right: last bottom plate cleaning sheetThese are all bottom plate cleaning sheets4x6 photo paper after bottom plate cleaning & all other cleanings4x6 photo paper after all cleaning and avoiding paper abrasion setting