Savannagh,I was just wondering did they send you all the correct parts, or any parts missing for the cage attachment as like you say no one else seems to have this problem (that doesn't mean you don't though)
If you need to check parts, I have this video on the silent runner wheel and attaching it.
https://www.youtube.com/watch?v=0QudWsqJiPU&t=1s
I don't know what else to suggest, unless you can attach a photo so we can see what is going on.