I have modeled a plastic cover as shown in the attached file. The plan is to make a prototype using FDM technology first then ejection molding for mass production. The part is symmetrical along vertical axis therefore I modeled half and used mirror body along right plane. The problem is that in the mirrored half showing problem in displaying some surfaces!!! I don’t know if this problem is only a display issue or it’s actually missing surfaces. When I export the solid part to a separate file as one solid body and use check command it does not show any missing surfaces. I tried delete faces in the problem area and use patch but not able to get the desire result.  The puzzling part the original half does not show a problem only the mirrored one. When I rolled back the features I can see that the problem is occurring after (deform 3) i also attempted to change some features but no successes

I would appreciate any help or feed back to resolve this issue.