Should the maxi cosi be wobbly when attached to the pram?

[SarahScot]

I have a Hauck Infinity pram that I boight 4 yrs ago when DS was born. I didn't ever like the carseat that came with it so have bought a maxi cosi cabriofix to go with it. After much searching I managed to find the adaptors on German eBay. However, when I fit it all together the seat can be wobbled back and forward by hand, although it doesn't move unless you push it on purpose IYSWIM. It doesn't feel like it could ever come off, but you know how super-careful you are with newborns!

When I used the Hauck seat and adaptors I don't think it moved. Does anyone else's (of any brand) move like this?