Hello- It looks like your object is not closed- that might be at least part of the problem- run ShowEdges > Naked edges to see where there might be gaps - closing those would be step one I would say. You can SaveSmall and then zip and sent it to tech@mcneel.com for a look as well.
Ok so now the edges are closed I think I have tried almost every combination to cut but I end up with the cutting line being attached to one side of the part …which setting do I change to get rid of that and just leave 2 parts cut perfectly ??