Brush roller keeps spinning in selector's hose position

With the floor/hose selector in “hose” position and the vacuum upright, the brush roller keeps spinning, threatening to overheat the motor and thermal cutoff occurs. I cleaned every accessible part of the vacuum (already clean and unobstructed) and repaired a small felt piece that cushions the roller against the bottom plate near the drive belt. The belt seems fine.

The brush roller is supposed to be still when the vacuum is in the upright position and “hose” is selected. How to repair?