This gets even worse when mixed in with emails, I recently bumped heads with the naming limitations as the naming of invoices exceeded the limits and rendered the excel file useless (it "existed", it would just error if you tried opening it).

File name limitation in 75 characters, so now my system renames the file when sending them by email to just the invoiced clients name, and retains the properly formatted one in the folder structure (It's a very detailed one following a "<course code>-<course name> <course date from and to> <student name> - <billable company>.xsl" pattern as it revolves around certifications and needs to follow certain regulations, and obviously exceeds 75 characters with ease)