Front fan on 650D has started to rattle

Few days ago, I noticed a rattling sound coming from my 650D. Turns out it is the front fan but it only rattles if the fan controller is at max speed and the front dust filter is attached. If I remove the dust filter but leave the fan controller on max speed, the noise is gone. If I leave the dust filter on but reduce the fan speed on the controller, the noise is gone. Basically, the noise only happens when the dust filter is attached and the fan controller speed is set to max.



Any ideas?