Error codes -43 and -50 when copying files to a connected print server

What you are trying to do should work, as you already know. But complicating the picture here is the fact that you are running Clean My Mac. That utility, while praised by some for helping them keep their computers "clean," has been implicated in many anomalies and problems posted by scores of people in these Discussions. One problem seems to stem from the fact that sometimes files that are otherwise needed by a program or even more seriously, by the operating system, can be deleted by Clean My MAc.

I see one of your error messages refers to files that "cannot be found." Something has possibly been deleted that the operating system needs to copy files to your server. I can't prove to you that this is connected to Clean My Mac, but it sounds like a possibility. After all, "cleaning" a Mac involves deleting files.

I would restart again in safe mode, or alternatively boot into Recovery and run Disk Utility from there (First Aid). Safe Mode does the same thing but also resets some caches, in case something in the cache is impeding operations.

Another thing to try: see if the problem persists with another user (you can create a new user if need be for this test).

If something has been deleted that is needed, you might need to reinstall the operating system, which is doable from Recovery as well. This would not involve a reformat or loss of any user files, simply a reinstall so that any missing operating system files get reinstated.