I am pretty new to Poser (you probably guessed).
They both have IK chains and I think I've found the cause. But not sure the best way to fix it.

It turns out that the thighs of Bloo and my hedhog nose have translation dials (x,y and z) in Poser. They don't come into play in Poser when posing unless you use the dials. But in Carrara they do. In carrara I can disable their influence in the Translation properties and everything then works.

But what is the best way to remove them in Poser. Do I have to edit the poser file with a text editor? Why have these parameters appeared for these joints and not others?