Diopter adjusting Knob on 67II AE Finder

My diopter adjusting knob on my AE finder becomes a bit loose. I

remember it was much tighter last year. I even had difficulty to turn

it. But it suddenly became quite loose one day. I am afraid there is

something wrong. It still adjusts fine. But it is so loose that I am

afraid it may fall apart someday. Can anyone tell me if your adjusting

knob is loose? Does it matter to be a little too loose? Is it

something easily fixed? My AE finder is just like a brand new one. I

am reluctant to experiment trying to take it apart unless it is fairly

easy. Any advice is appreciated.