Hah, the README says:
> Additonally, debugging may not land on the macro statements themselves.
See my comment above, and give int3;nop a try.
Interesting. Unfortunately, I'm not well versed in assembly, is there a similar trick or requirement in arm and would that include Apple silicon, or is this something specific to `int3` on x86? That may explain why it was inconsistent during my development process, I didn't think to check if the inconsistency was platform dependent.
Answering my own question, apparently `brk #1` is insufficient on Apple silicon. That results in just a trap and will prevent the debugger from continuing past the debug statement. From a bit of searching and my experiments `brk #0xF000` was the way to go instead which had the consequence of not always landing on the debug statement, the addition of a nop with `brk #0xF000 \n nop` resulted in the debugger landing on the correct statement.