UploadedFile->move() unknown error

I recently upgraded to Laravel 7, and found that file uploads that had been working on previous versions were throwing an error:

[2020-11-11 00:08:18] local.ERROR: The file "temp.jpg" was not uploaded due to an unknown error. {"userId":1,"exception":"[object] (Symfony\Component\HttpFoundation\File\Exception\FileException(code: 0) : The file "temp.jpg" was not uploaded due to an unknown error. at /var/www/dev-events/vendor/symfony/http-foundation/File/UploadedFile.php:213) [stacktrace]

It's specifically a call to $file->move($oldpath, $newpath), which ends up logging that error.

Any known issue with that? I did move through 5.8 to 7 fairly quickly, so it could be something I did or overlooked in the interceding verions.

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