Apparently you are not operating the machine correctly. It is NOT a "Swing machine" and should not be used with a side to side motion.
From my manual-
How to operate the roto for best results. Hold the machine firmly, and turn the motor on. Quickly find the neutral point where the machine is not moving, just turning the bonnet. Instead of lowering and raising the handle, making the machine go to the left or right, keep the handle level at the neutral point, and push it, then pull it, so the machine describes an oval. With a little practice, you can totally control the machine's movements without it getting away from you.
As you make the oval motion with the machine, overlap at least 1/3 of the prior oval. Making the next row of ovals, overlap at least 1/3 of the prior row.
Make a row to the left or right, go back over the same area in the opposite direction. This gets all sides of all the fibers for the best cleaning effort.
If you raise then lower the handle, and make wide horizontal passes, the effect is on the carpet making a heel and toe pass, and the center of the pass is not cleaned the same as the edges. This also is much harder to groom out, and when dry, in some cases there are clean then dirty streaks, which are much harder to remove in the future.
With the oval motion, the entire area to be cleaned is the same on all sides of all tufts, nothing is missed.
9. After doing about 100 sq, ft, remove the bonnet and look at the down side for dirt. If dirty, turn it over, if not, keep going. About 100 sq. ft for the second side. Then the second bonnet to finish up.
10 When done with the job, launder the bonnets in your washing machine, but not in the dryer- just let drip dry, hang on a line, etc to dry.
E-mail me if you want more info.
Gary