The texture is striped because a 3D wall is in fact made of two thiner walls one for the left side and the other one for the right side. The strips appear in the 3D view when the two sides don't have the same color and are very far.

I fixed it in Sweet Home 3D 2.3 Beta, by removing the useless parts in the middle of the wall.
Don't hesitate to test this change on many SH3D files to check I didn't miss something.