[Q]Brep&Plane and Brep&Brep Intersection fail !!

Hi fellows,

I have one untrimed surface ,then I divide it into 196 sub-surfaces .these sub-surfaces are untrimed surface of course . After that , Brep&plane Intersection component is used to get results for further operations .In my logic ,the results of this step should have to be "Null" or "Line-like curve/Line" or "point"(The 196 surface are planar in this case ), isn't it?? Four "invaild curve" data ,however, appear !! Does this make sense ????

I check the four surfaces which generate "invalid curve" ,I found nothing special from others but only very little surface of them touch the intersection plane . I guess it's some tolerance quections??

P.S.  As the followed picture shows, the four holes stands for the four planar surfaces which output invaild data .Thanks for help in advance.