Sometimes it so happens that a user cannot view the values of a managed metadata column, even if the user has been granted permissions to the library or file. This simply means that the user is still missing permissions, how strange this may sound. The cause? SharePoint operates with a hidden list in which it stores all metadata for the impacted sitecollection. And as it may turn out, your user doesn’t have access to it!
In some cases, when you work with Excel-documents, you’ll stumble upon the Excel-error “Cannot perform this operation. The file has been deleted or someone else has it checked out.” somewhere down the line. Now, there could be a tiny chance that the file you’re working on actually has been deleted or checked out by someone else. But chances are much higher that the error is caused by something else.