Why is the brush roller sticking for v6 vacuum

Why is the brush roller sticking for v6 vacuum

teeth on lower roll insert that can interfere with teeth on the housing. My brush roll will not turn when re-installed. It installs easily, powers up, spins about 4-5 revolutions, then shuts off power for a second, then comes back on without roller spinning at all. I can see it is the teeth interlocking but don't know how long it makes the first 4 or 5 revs.