minimise.txt
This fails: <paste the code and the failure>

Help me reduce it to the smallest thing that still fails. Give me an
order to remove things in — largest and least likely to be involved
first — checking after each removal that it still fails.

I want to end up with something under 20 lines that reproduces it.

If removing something makes the failure stop, that's the interesting
part — tell me what to conclude from that.

The reduction usually finds the bug before you finish. Roughly half the time you never need to ask the actual question.