[Brightcolours]

Sorry, I'm very late.

 

The diamond shaped reproduction is likely a result of pinched optics, basically a lens being held in place too tight and causing a physical change in the element. 

 

re: "You don't get astigmatism shapes when you are that defocussed"

 

Astigmatism is present at all focus depths, onion ring bokeh is one manifestation of astigmatism.

Onion ring bokeh is just a sign that an aspherical element is not totally smooth... "production" marks.

And pinched optics?? Really? No.