mesh problems in CST

Dear readers ...
I am MTech student i am working on displacement sensor using microstriop antenna and SRR technique.
when I moving the SRR above the feed line from 0.1 to 0.4 mm the program sends an error massage, it says that : ( port 2 is inhomogeneously filled with first 3 mesh cells . cannot start solver ).
what did that mean and how can i solve this problem ?
my best wishes..

You should set the boundary conditions to open(add space).

i am doing it .