My new observations:
– ^A, ^B, ^F, ^Y don't have meaning: replacing them with A, B, F, Y
doesn't stop core dump
– the "ndash", .i.e. this char: >>> – <<<, has a role, because
replacing it with other char, also one like §, stops core dump
– length of the string has a role, tired shortening the string on the
left and no core dump then

I attach input2b.txt with no control chars and test2.zsh (zsh -f) that
opens that file

Best regards,
Sebastian Gniazdowski