Asymmetric Pattern of Quad Ridged Horn Antenna

Hi, I have designed a quad ridged horn antenna. Everything is fine, gain, sparameters, etc. However, E-plane pattern of each port has shifted 1-2 degrees. It is because of the asymmetry of quad ridged waveguide feed section. This is caused by the phase delay due to other prob's enterance. When I use the connector having small external radius, the shift decreases. However, I should use a specific connector, therefore I need a techniques to get rid of this asymmetry.

Could you give me an advice on this issue?

Regards..