Nikon d90 + sp-900 problem

I have Nikon d90 + flash sp-900 sometime while taking pictures my flash dosn't read and thare is no focus! I have to posh the flash a lil bit to the left so the camera can read it. I want to know what to do with thise. I tried another sp 900 and the same… But when i try sp-800 its more stable on the camera and thare is no space to move… I have these problem on 2 Nikon d90's cameras. And i need a fix.

Are you locking the flash into the hotshoe? Not just sliding it in, but actually engaging whatever sort of lock the SB-900 uses?

If you are, and you are experiencing this problem on mutiple bodies, then the shoe on the SB-900 is bad. Since this is the 1st time I've heard of this problem, I'm not thinking that is the issue. If all SB-900 shoes were bad, we'd have heard about it by now.

Thare she blows her focus?

Tha flash is a lil bit not talking with da camera. Start by cleaning the contacts.