This is useful to work out whether variable A & B were both set wrong, or variable A was set wrong and variable B was set correctly, but based on that wrong data. Meanwhile, tools like LogRocketopens in a new tab let you replay user sessions to see what they saw, and understand issues you can't reproduce accurately yourself. * Network issues (especially DNS) * System time set wrong (that one's caused some really weird issues for me) * Antivirus interfering * Filename casing (e.g. case sensitive on linux, but not mac or windows)