DIAGNOSIS This is a ‘streaking’ issue. The DuoClean brushrolls are not contacting the carpet evenly, often due to height setting or a clog between them.
FIX Adjust the height setting. Ensure the floor nozzle dial is set to ‘Carpet’, not ‘Hard Floor’. On thick carpet, manually lift the handle slightly to help the nozzle adjust. Make a second pass over the streak.
IF THAT DIDN'T WORK A clog is trapped between the front soft roller and the rear bristle brushroll. Power off. Flip the nozzle. Remove the cover and clear any packed debris, hair, or string from the channel separating the two rollers.
HEADS UP This vacuum performs best with overlapping strokes. Do not use rapid, short jabs. Use slow, deliberate, overlapping forward pulls.