I did get this on my localhost install, which I though was odd with one file only (copy and paste) job of files from one folder to another. Deleting file, then downloading zip again and copy that file over fixed it. But I'm sure the file passed File Checking at first, then later failed for some reason even though nothing had been edited in it by me.
I just did a clean install today and I got the same. I downloaded 1.1.2 today and installed today. After file health check I have the same "library/XenForo/Model/Permission.php File does not contain expected contents.".
I re uploaded from the zip file and the same. What to do ?