File called OAuth.php won't publish

When I publish my web site, the file called OAuth.php fails to publish and times out.
I never had this problem under Catalina. It has only begun since upgrading to BigSur.
I can’t even use FTP to copy the file from my LocalFolder. Again it fails to copy.
Any ideas would be most helpful.
I am using the latest versions of everything.

This would be best answered by @ben, @dan, @tpbradley.