Port settings with normal component fields (possibly a bug)

Hello,

I am trying to simulate a structure with oblique incidence. From the port settings, I have noticed a possible bug in COMSOL.

Please take a look at the attached screenshots: for all other settings identical, if I setup the port with the magnetic field, it works well. However, when I setup the port with the electric field, I get errors where the port doesn't function as it should. Note that this is 2D simulation where the port is parallel to the x-axis, and I am simulating a TM case. I can simply use the H-field in the port settings, but I think E-field setting should work as well. There are instances where I launch a mode that is neither TE nor TM with respect to the port in 3D simulations.

My guess is that whenever there is a field component perpendicular to the port surface in the port settings (y-component in this case), the port doesn't function well: this is the electric field case.

I am not sure if I am mistaken or this is a limitation of COMSOL.

Thanks.
Young Mo