This happened to me too and it took me a little bit to figure it out. You are talking about the small gears right?

They don't wedge or pop in if you have tried that. All you have to do is place them in there so they are touching the other gears they normally contact and then spin....the axle I think.....while holding the small gears in place so they will be sucked into the correct position.

It's been quite a couple of years since I did mine so I apologize for the somewhat vague answer. I honestly don't remember if it is the axle you spin or something else. But you should be able to figure it out from what I wrote.