I snagged one of these off eBay. It's used so I actually started with a visual inspection. I noticed more dust on the fan than I was comfortable with so I took the fuse out and unscrewed the cover, then the shiny fan screen screws and cleaned it off. Took a cotton swab around on the inside when I noticed some of the blades were not in their tracks molded in the case and even touching the adjacent blade.
I took the cover off the other side and pushed the whole unit out from the connection side to re seat all the components in their tracks. This was a little tricky, if I got the bottom going to far ahead the blades got hung up or the opposite would happen when the blades got ahead. But eventually it slid in place nice and smooth.
However, it seemed like when I set it back upright the weight of the blades in the center caused the controller board to bow slightly to the point where those blades would pop back out of the tracks again. I could see where once the device was up and running and generating heat that the controller board would lose some rigidity and the blades popping out easily. I spent maybe 5 minutes thinking of what I would stuff under the controller board to support it when I did the V8 forehead slap and said to myself, Just turn the damn thing upside down. Viola, now the 6 study heavy heat sink laden blades support the light controller board and gravity keeps them in their tracks.