Cause

The toner shield glass is dirty.

White streaks appear because the toner shield glass is dirty, which causes the radiated light to be uneven.

The charge unit is dirty or has reached the end of PM life.

White streaks appear because the charge unit is dirty or has reached the end of PM life, which causes the charging to be uneven.

Foreign object stuck in the development unit gap

White streaks appear because there is a foreign object stuck in the development unit gap, which causes the absence of toner on the development roller.