Is the noise more of a screech or rattle/vibration?

Does the motor shut down when this happens (i.e. trips the thermal overload)?

If not, then the motor is probably not binding and it may be just the brass nut in the impeller has come loose/broken so it is slipping on the shaft of the motor. This would cause wobble and tear up the impeller ring plus make a lot of noise. When you turn the impeller, the motor shaft should turn too.

If the motor is shutting down, then it probably is a bearing although other things can bind the motor shaft including the impeller and/or impeller ring.