DIY Assembly

[byu]

So, I'm trying to assemble my PuzzleProz type A speedcube, but as soon as I put together the pieces, one lift off my table and everything just collapses. Is this because my center pieces aren't tight enough, or am I doing something else wrong?

 

[Odin]

http://www.youtube.com/watch?v=dtkGze92bRk hope it helps!