Basic Question about ON_Mesh in c++ sdk

Once i moved several vertex (single and double precision) and recompute normal , compact …
my valid mesh added to rhino behave with a kind of clipping plane in viewport (i’m in rh8) if i move a vertex from rhino with gumball
my mesh re become normal again is that a bug or did i forget to call a method in fact this happen only if i’m move m_dV and m_V of my ON_Mesh object, i have just reset both values to new on few points.

the ON_Mesh::Cleanup() method fix the issue.