Diagnosis
The mopping pads are either saturated unevenly, worn out, or the oscillation mechanism is impeded. Streaks indicate inconsistent pad contact.
How to Fix It
First, replace the mopping pads with new, official iLife pads. Third-party pads are often thicker and impede oscillation. Second, manually rinse and thoroughly wring out the pads before installation. They must be damp, not dripping. Third, during operation, verify the gray pad holder is oscillating back and forth slightly.
If That Didn't Work
Debris is trapped in the tracks of the oscillating mechanism. Turn the robot over and manually move the pad holder left and right. It should move freely. Clear any hair or grit from the sliding rails.
Heads Up
Using too much cleaning solution or solutions with oils/waxes will cause streaking. Dilute per instructions and use only solutions approved for robot mops.