I cannot relate to what 99 decibels sounds like but looking at this chart
that sounds very loud.
They are a smaller motor than some other models and usually are not loud enough to comment on. So, I suspect yours must be louder that usual.
As it has had a hard life, it sounds like the bearings may be worn. That tends to cause motors to be noisy. A replacement motor would be the easy solution.
However, we had one a few days ago that came in with a suspected motor bearing issue, and that was very
Turns out something plastic had been sucked down the duct housing (and the cyclone has to be off for that to happen) and it had lodged at the motor inlet and was catching the blades. That made an awful
I would strip it down and bench test the motor and take a view then.