Invalid brep with surface morph

Hello, Can you tell me how to apply the following pattern on a curved surface, I used surface morph, it actually gives the wanted result but as an invalid B rep, any explanation would be helpful. Thank you.
invalid (50.9 KB)

You can avoid the invalid brep condition by using slightly less than the full ‘U’ domain.

invalid (50.1 KB)

That solved it indeed. thanks

The slider can be set very low, less than 0.001 to get a closed brep. Negligible visually as long as you remember you have created a “hole in the boat” so to speak. In some cases, that can matter.