A fun problem on a Mac is that if you're using APFS for your filesystem, if it fills up, you can't delete any files. It's caught me out a handful of times, and each time, the only way to recover is to reboot, and thankfully I've had more free disk space after a reboot.

I'm not going to try to understand the logic as to why APFS requires free space in order to delete files (via any method, including dd)