[Moved]： Problem with periodic boundary condition in CST

Hi every one
I have a problem with periodic boundary condition in CST software.
I have a cylinder with two layer coating which is infinite along z axis
I used periodic boundary condition for z
This warning occured:
Inhomogeneous material at periodic boundary detected. Farfield results may be inaccurate. (The structure must be identical in the periodic boundary plane and the next two mesh steps.)
Location(s): zmin zmax
What should I do? Does it mean that I can't use PBC for my structure?

hi
please upload ur project.