I would agree. A classic upright which has no option to turn off the brush roll should never be used on bare floors as the bristles and beater bar are not designed to remove dirt from a bare floor surface. In fact, the spinning brushroll is counterproductive on a bare floor and has a tendency to scatter and blow dirt away, rather than sending it up into the suction path.
Maybe the beater bars are hitting the bare floor in certain places, or hitting thresholds between rooms, or edge hardware? Or maybe your have a bump or warp in one of your floors that the brushroll keeps hitting, thus straining the belt?
Truth is, if you don't use this on carpets, you don't need the brushroll. Remove the belt and brushroll and let the suction do the cleaning for you. Problem solved.