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Okay, so I didn't figure out why it behaves like it does, but why it occurs and how you can work around it: your pattern is identical under a 180-degree rotation, and thus confuses the detector (hint: check the corners).

Generating a pattern with the two "pointy" corners on the same side of the rectangle (i.e. not opposite of each other), and the "rounded" corners with the two circles on the same side of the rectangle (i.e. not opposite).

For example, compare your images to the one below (Generated with -r11 -c4 and rotated to fit here). Here the "pointy" corners are up, and the "rounded" corners of the pattern down. If my description of the corners is still unclear, imagine drawing the convex hull around the pattern, and you'll probably see :)