You have very keen eyes! Yes at the slot the extrusion is 0.15mm low both sides, since the outside flat is shorter than the centre flat it must be at a slightly steeper angle. I have measured and calculated the cant angle the 15mm profile would have as 0.055 degrees or 198 arcseconds, does this matter (it will be mirrored on the second rail).

Or should I just man up and hit it with this:
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