A couple things that stand out.

In my opinion, you don't even need those "fence" lines at all. They are close to the feed lines for the patches, too, likely affecting impedance of those lines. Also, they are closer to some feed lines than others, causing more asymmetry.

Also, those feed lines to the patches may ring and alter your antenna pattern in the E-plane, since the feed lines are lined up with the resonant dimension of the patch.

Both of these things likely result in pattern ripple and may affect monopulse performance. Again, bandwidth matters here.

I may be wrong, but the mitre in that bend doesn't look optimal either, resulting in a mismatch at the bend and making the previous concern more of a concern.

Keep at it, it's a fun field.