Welcome to the forum!

Are you using Windows Finale?

Windows Finale v27.1.0.271

It's a problem with "Make Backups when saving files". Turning this option off makes the error go away.

As you can see, that is a path issue. You want to use the Submit a request link at the top of the page to send this to MakeMusic Support.

I have to ask, in your preferences you have a backup folder specified that already exists?  Finale will not create one.  You must do that manually yourself.

I never (in 20 years) have had to create those folders. Did you assign them somewhere else? What does it say in your preferences?

Yep, me neither... Preferences pointed to "Finale Files" in my OneDrive.

Now, how about an error message that actually HELPS me fix that?!? Instead of Error Id moving file "s" to "s". Something like, "Unable to write to Backup Files folder" might be useful.

For future reference, make sure your preferences (Edit > Preferences > Folders) point to valid folders that already exist.

Preferences pointed to "Finale Files" in my OneDrive.

I don’t believe that Finale knows to store files in the cloud. You have to specify the full path — and your internet connection has to be both robust and fast enough so as not to time out.

https://support.microsoft.com/en-us/office/sync-files-with-onedrive-in-windows-615391c4-2bd3-4aae-a42a-858262e42a49 

OneDrive is almost certainly the problem. I just read an articulate rant about recent changes that Microsoft has made to it. Chief among the issues is that it can move files from your Mac or PC to the cloud without warning, so the author claims. Sounds like that may have happened to you.

Unfortunately, I'm now on a different computer and cannot find that article. Here is the Microsoft Support page:

https://support.microsoft.com/en-us/office/fixes-or-workarounds-for-recent-issues-in-onedrive-36110213-f3f6-490d-8cb7-3833539def0b 

When it installed as part of Office 2019 a couple of years ago, I took a look and immediately removed it. Glad I did. 

I know the OP is on Windows but this just came in today. Dropbox users (like I) should pay attention as well.

Don’t install the macOS 12.3 beta if you use Dropbox or OneDrive

https://www.cultofmac.com/765384/dont-install-macos-123-dropbox-onedrive/ 

I had this same problem(in Windows). But when I opened Finale as Administrator it didn't happen again.
So what I understand is that there was a writing problem. I checked the folder and it was read only. I changed the option and the problem was solved.

(note: This happened to me when I activated windows defender ransomware protection, this blocks access to the documents folder.)

Thank you.

This last entry by Andres was the solution--I am using Windows 10, Finale v27

:-)
Nessa