The head is bad. Common issue on the DC28. You have to replace the whole head you can't work on it. I know it sucks but it's extremely common on the DC28.

U need a base plate

btw it does spin in upright some times its normal

The air mussels suck I had to repair so many on those for my teachers

What ended up being the fix in the end? I replaced the head on mine and still getting red flashing light. Gota main board on order.

I'd love one of those. How much did you pay?

I googled the manual. It means the brush is jammed somewhere