Drilled holes are nowt to do with it.
The deep scoring (poor machining??) hasn’t helped. It seems to have broken along a score mark not at the change of section (or is it my eyes/quality of picture).
I’ve not had my ESA apart for years, does the thread on the crankshaft go to the end of the nut? If it does, I don’t know how it breaks there, other than tightening/slackening. I’m a bit concerned that I use an impact driver to release mine – I’ll have to check it next time I’m in the area.
H