Assymetrically placed Close in side lobes

I have designed an 8x8 probe fed rectangular patch antenna array with the aperture amplitude distribution corresponding to Taylor 30 dB side lobe level. The patch elements are loaded with U-shaped slots to enhance bandwidth. The power divider network is realised by means of corporate feed-unequal split wilkinson power dividers.

The antenna exhibits a gain of 20 dB and a side lobe level of < -24 dB except for two small peaks at -18 dB in E-plane only on one side of the main beam. The other side of the main beam has low side lobes of < -24 dB. Could someone throw light on this as why these asymmetrically placed close-in sidelobes arise?

Thanks.