When the bunter is broken how does the right angle bottom bar morph into the 45 degree angle PI shape? Also should we not see an equal number of II stamps with the top bar broken if this is a result of a defective bunter? My tuppence.
The 45° angle you see likely is because the edges do not break in a 90° angle.
I assume broken bunters where the writing (i.e. the “ridges” of the bunter) is breaking off is the result of impropper hardening of the same. Depending on how these get hardened it may be that hardness is changing every single mm in a bunter - thus allowing parts to break and some parts to remain functional.
And as we see usual the bunter parts where the radial forces are stressing the bunter (as per nature of the hs forming process - usually not being stamped later as so many people thing).
And I assume broken bunters got exchanged as soon as QA noticed, so qty of these hs should be not all that much.
You can see an example of a top bar broken in the picture posted above (first image, left column, bottom).