Surfaces randomly disappearing in my part.

I will be working editing my injected part, and ill insert a fillet or pattern, and then ill notice that some surfaces randomly disappear?

This is a huge problem, because then i need to go and create a fill for each missing surface. Is there a fix for this? It seems like a huge problem.

Is it just that my geometry is terminating the surface that is disappearing?

Keep in mind that my part is not a surfaced part, it is solid.

All input is appreciated.

SolidworksPlastics And Mold Design