I have written a method which (like a knife) cuts parts off a model even if the model has nested groups.  It works well in most cases, however not always. The problem has to do with certain groups.

Consider a model comprising two groups where one was created by copying the other.  Both contain the same 5 entities.  (They are rectangles).    SU "Entity Info" says "Group. 2 in model" (which may be a bug in SU? )

I "opened" one group (in SU) and deleted an edge then closed the group.   The display was as expected but but when I examined each group in turn with      Sketchup.active_model.selection[0].entities.count I found that BOTH groups had  3 entities.  Surely the untouched group should still have 5 entities? In fact whatever I did to either group affected both - very like editing a component.

Can anybody shed light on this please?

(It is annoying because the same happens if the deletion is done in Ruby.   If my "knife" method comes across such "twinned" groups it must somehow un-twin them before deleting anything from inside either.  The Group::make_unique method helps but is inefficient as it seems to duplicate all the entities, and also is deprecated.)

I have performed the above tests many times and sometimes the error has shown up differently. Sometimes the display of both groups is altered.  Other times the entity count has remained at 5 for both groups.