This warning appears at the top of all admin pages in the Community Survey component:

Warning: fopen(virtualcron.txt): failed to open stream: Permission denied in [redacted]/components/com_cjlib/framework/virtualcron.php on line 53

I'm not sure how problematic that is, but I hope there is a way of getting rid of it. I've tried changing ownsership and permissions on virtualcron.txt,  but nothing makes that warning go away.