It is strange that this took 5 days to find. Simply because of logs.

Go to logs. Filter by errors. Oh, errors in insert subscription. Seems relevant.

I could understand if the errors were somewhere else.

Even if logs didn't exist. Problematic endpoint generating 50 emails per day? I would have immediately thrown a try catch and rendered the error to the user if logging was impossible. Then your very next bug report solves it.

Assuming that they had the error (guid collision) - it's not as easy to spot as some commentators are making out. But surely after reading the code s few times.

Ironically they should have asked ChatGPT for help debugging