1.) clean the fan
2.)spin the fan manually and see if the fan is hitting anything
3.)see if there is blades bent or positioned in an off angle compared to others
4.)perhaps considering getting a new fan?
Carefully squish the blade hub onto the bearing firmly, it may just be a touch loose,
And isn't your tagline a misquote?
Always thought it was he who understands the past controls the future? No worries just random wonder hehe