Weird. That's a wired keybioard, not wireless so fan radio frequency noise is not a problem.
Suggest you move the electric cord from the fan away from the wire used by the keyboard. Assume this is a noise problem coming in thru the USB cable, not anything through your PC's line cord.
Do you have anything funny plugged into the same USB hub as your keyboard that might be affected by radio frequency noise from a fan ? Maybe the fan kills your fitbit bluetooth (or whatever) and it kills the keyboard as it goes. Maybe try removing other USB devices if moving the cords doesn't help.
Do post what it turns out to be.