We just had the same Problem with the Roomba S9 from Costco after only owning it 4months. We had the "Clean Brushes" error pop up about 6-7 times in a row and it was very frustrating. The first time it errored out, there was actually hair to clean out, but the other 6 or so times, there was nothing.. I believe the problem comes from when you clean the two green roller brushes and put them back into place that they are not aligned right. (Maybe a design flaw?) After the last time that it happened, I just turned the robot over and turned the front roller about an 1/8" to 1/4" and it has not errored since.