CST MWS Radiation Efficiency vs Total Efficiency

Hello,

I lived a problem about waveguide simulation.
İn this waveguide there are 3 output ports.

Radiation efficiency result is nearly -0.01 dB of first port.
S11 result of this port is nearly -15 dB.
But total efficiency result is nearly -6.5 dB, So realized farfield gain result is effect beacuse of total efficiency is bad.

For example, the other port(second port) is nearly -0.01dB as radiation efficency on same waveguide.
And S22 is of second port is nearly -10 dB.
Total efficiency is -0.5 dB, I think, this result is normal as total eff.


Do you have any idea about this situation.
What can it be efficient nothing less S parameter as a result between radiaton eff and total eff on waveguide simulation?
And On a waveguide two output port result offer different result between radiation eff to total eff.