Most bugs are from the head to desk variety or simple oversights. In those cases I'm so happy that the users never see the code. Those bug are annoying but boring. Other bugs are so much more fun.
A user opened a ticket that he couldn't write a PDF file. He is using BoxCryptor, which adds another layer of encryption to your already encrypted cloud solutions like Dropbox or iCloud. I saw exactly where the problem happened but I wasn't able to reproduce the problem.
The user got another laptop with Catalina. Here the problem was slightly different. The containing folder of the PDF couldn't be written. The error was typical for the current macOS: an unknown error. But I finally had the correct idea what might cause the error. A so modern Emoji in the email subject.
The user tried to copy the email as eml file to the BoxCrytor folder and there we had it. BoxCryptor doesn't support Emojis in the file name.
I opened a ticket with BoxCryptor and already got a reply that they are working on the issue. I was told the Dropbox only supports a character set standard from 1999. That means no Emojis at all. Can anyone remember that time?
For now the user will get a custom build that will eat all characters that are outside the German characters. With that he will be able to archive.
A more general solution will be more complex. But so far the problem hasn't come up. Killing all Emojis in the PDFs from Mail Archiver isn't a good idea. Killing them isn't as easy as it sounds, by the way, because the modern character sets are huge beasts.
Then there is the utter helplessness of the unspecified error from macOS. If there is a specific error then I can react. An unspecified error could mean anything.
What might make sense is to try to detect Dropbox and BoxCryptor and then kill the so important Emojis. If I'm bored I could make a ticket with the Dropbox folks. My experience with their reactions to tickets hasn't been good. I also can't imagine that fixing the problem on the BoxCryptor side will be simple.