> Seeing your code work on another computer tells you nothing at all
Oh, it can be quite useful. "Another computer" often means "a system that has not had the interesting local undocumented developer modifications that have replaced basic perl modules with too-new or too-old CPAN dependencies". Or it can mean systems that have not had the latest software update with the new regression in a system library, or a system where a developer has not been tuning sysctl parameters and SELinux. I've run into all of those, in the last week.
I'm afraid I'm unable to post some of my best failures, they're too personally identifiable to me or to a client or colleague. I will mention my most galling, most frequent style of bug in the last five years: It's the complete refusal to bundle software. To just "compile from source" or haphazardly integrate components from CPAN, from pip, from maven, from apt or RPM or other sourceforge or github or any unmaintained, untested repository scattered anywhere in the world without the slightest dependency testing or component verification. Cleaning up the mess is paying a great deal of my salary right now.