Appending Groupnodes to an already existing Groupnode structure?

Appending Groupnodes to an already existing Groupnode structure?

Question: In Poser, is it possible to add an extra morph groupnode hierarchy to an already existing hierarchy in a Figure (V4 DAZ) through a pz2 injection? (during runtime obviously)

for example:

original:

Code:

groups
{
    groupNode Head
    {
       ParamNode Smile
    }
}

in the pz2 injection:

Code:

    groupNode Customgroup
    {
       ParamNode OpenMouth
    }

after injection:

Code:

groups
{
    groupNode Head
    {
       ParamNode Smile
    }

    groupNode Customgroup
    {
       ParamNode OpenMouth
    }
}

I am making an Injection and right now its is working fine, except with some users it entirely replaces the original V4 group structure (including Morph++ groups), which is very impractical. But with other users it just gets appended.

There's no clear evidence to say that it is a version issue, perhaps it might be an update issue? It doesn't work with my Poser Pro 2012 but it does work with a friend's 2012, it sometimes works with 2010 and doesn't work with 2008... why is this?