This fix may not be permanent and the problem may come back. Replace the board or potentiometer if this happens. Let the switch dry for 1 hour before reassembly.

If you do not have zipties available, tuck the wires in the fan so that they cannot easily move. This can be used as a short term solution.

Wipe off any excess contact cleaner on the PCB. Reinstall the board once the contact cleaner is dry.