Omega Altise Tower Fan Squeaks loudly when oscillating

Fan squeaks loudly when oscillating. I have tried taking the back off the fan (to see if it might look similar inside to previous response on squeaking fan). However could only find 4 screws and it does not seem to want to separate from the front of the fan easily. I am not sure if the cap on the top of the fan needs to come off first (cannot see any screws). I have tried vacuuming through the fan grill in case dust was the issue - this did not make any difference. Can you advise how someone without any technical expertise might be able to stop the fan squeaking please?