Hi 
I try to correctly understand the operation of “ZifA” with the use of a character whom I try to articulate as in poser for example.
I know that much works on this handling which remains very mysterious, and oddly no explanations on this subject which however seems one of the most advanced tools of Zbrush.
I find npt reponses in the posts precedents and god alone knows that I visited some.
here, one above good once for all can to be clear it?
exist there fixed rules allowing to avoid the errors which you see on the following images.
as you can note it here is the type of error which I meet.
and that without reelle logic, few times for an identical rotation of a member, the result will be different.
And that does not arrive systematically, some times I can practically move my character without many problems,
other times it be enough to a degree to rotation and poufff!! alls meshes crashed or it reset modeling.
all that appears quite hazardeux to me, I suppose of course that there is a logical explanation to all that
thank you 
