Follow these troubleshooting steps in order. They are ranked from simplest (least invasive) to most complex.
If the Read-only attribute is set on bigfile000, the operating system will deny exclusive write access. Even if the program only needs read access, requesting "exclusive" can fail if the file is flagged as read-only by the OS. unable to open bigfile bigfile000 exclusive
macOS’s APFS file system handles locks differently. Follow these troubleshooting steps in order