Vacuum Cleaner "Loud crunching noise" runs great without belt and rollerbar?

I have a Bissel 6594 Series Vac.

The other day we noticed a burning rubber smell coming from the machine. I turned it over and saw that the roller bar wasn't moving.We went and purchased a new belt replacement put it on and the burning rubber smell came back and this time the vac would make a noise as if there are bolts ran over. Like a crunching/grinding noise and loud. Took the belt and roller off and the vacuum works good. No noise problems and the attachments work good. Still sucks up things. I looked at the bottom of the vac to see if anything is caught but couldn't find anything. Even had my wife clean it out. Still the same problem.

Could this be the motor failing. Seems odd that it does the issues when belt is installed on the motor bar.

Any help would be greatly appreciated. :)