I've did debugging and removed all crashes found by me regarding face splitter. It still do not work completely right in File->Open case, but at least it removes the crases. Also, in case of crashes it does not give a huge messagebox meaningless error, but it will only fail this part of the document. This is grat mostly in case that are serialization bugs that happen when creating/applying an undo/redo operation.
It happen that because of various refactors, the propagation had an explosion of regenerations when happen a parametric propagation. This was caused that are two entities that store the shape that are equivalent form (the TopoDSInterpreter which stores the OpenCascade shape and NamedShapeInterpreter which stores the OCC View corresponding AIS_Shape). Right now it will happen only one of them, so right now just model notifications are emited for propagation purposes.
IronPython was removed as Lua offer everything that IPy has, only just Lua is better integrated, so there is no point to keep both.