Frank, if you compare your photo with the one posted by Jay, I think the bolt holding the bracket is in the area shaded yellow. the blue area is the upper bolt head in Jay's photo. If I am right, what you are interpreting as a crack is probably the top edge of the mounting bracket.
Thanks for the Detailed Investigation & spotting
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On second inspection, you are 'Spot On'. The 'Crack' is in fact the top of the Bolt head,
Phew!
Also thank you Richard - Aus for similar info.
