Oblique incidence and floquet condition problem

In the RF module, I found that there are 2 problems.

First,
When the thickness of the layer which uses scattering boundary condition gets thin (below ~200nm), the direction of power flow [sqrt(emw.Poavx^2+emw.Poavy^2+emw.Poavz^2)] doesn't go 90 degrees even if I set the incident angle as 90 degrees.

Second,
The power flow distribution reaches below some part of port condition area even if I set the incident angle as 90 degrees.

I also tested it in the plasmonic wire grating of model library which uses port condition instead of scattering boundary condition. However same problems occurred.

I attached figures of my question.

please help me.