Some patches are removed unwanted

[Mans]

I created this part of the car seat (fantastically). The majority of the segments are separated and when I try to joint the segments as one body, some of the patches are removed and it seems those are not organized with the edges of the segments.

Please tell me what's the cause and what I must to do to retain the patches?

The half of the seat has been doubled (with separate segments) by using symmetry

Then I used join and integrated the segments of the seat and you can see the result

 

[MrCATIA]

View + Render Style + Shading With Edges

 

[Mans]

Thank you senior, it worked