ok sorted the "clipping"
it seems re-imported models can lose a vertex here and there.
and a four sided textured plane,surrounded by 3 sided triangular ones kind of "shorts out" so to speak with contact
with other objects,like the ground,other body parts,equipment etc.
to get round this,isolate the 4 sided plane and "triangulate"
in o2.this is a feature in the (create) drop down list.