Hi,
On macOS the "?" character is allowed in folder names, unlike Windows where it's prohibited by the OS. The issue during MP4 export the most likely occurs because the "?" symbol is interpreted as a special character by video encoders, which breaks the file path.
I'll check the code if we can handle this case in a future update. Currently I recommend to avoiding "?" symbold in folder names.
Also please note that even if we add this support for macOS, the project will not be able to be opened on a PC with Windows.