Brush turning slowly while shampooing. It

Brush turning slowly while shampooing.

It starts out fast, but after a minute or 2 the brush is not spinning very fast.

I have powered it off and let it cool down. I just started out so I can't believe the engine is over heating, just doing 2 rooms, can't even get through the first room.
If I take the brush attachment off, then put it back on and then turn it on, it spins fast, but after a a few minutes, it's spinning softly/slowly again.
Kirby diamond edition