Hell, I don't submit help requests without a confident understanding of what's wrong.

Hi Amazon. My cart, ID xyz123, failed to check out. Your browser javascript seems to be throwing an error on line 173 of "null is not an object". I think this is because the variable is overwritten in line 124, but only when the number of items AND the total cart price are prime.

Generally, by the time I have my full support request, I have either solved my problem or solved theirs.