I don’t think the capacitor would cause this, it may be from an insufficient power supply. I would check the power supply first and then take a look at the power cord and connections. It may also be from dirt or debris accumulating in the fan housing blocking the vents that allow the motor to cool or the armature fan could be damaged. I am not sure what the exact design of this fan is but checking that the unit is clean, has a good power supply and good connections would be a good place to start.

If you can upload a picture of the Fan or possibly the model# that may give more insight.

- MTR