Unable to delete file in SharePoint Online
Recently I had a customer contact me with an issue in one of their document libraries, when they tried to delete a group of documents thru the GUI they got the error 'File not Found'.
As well when they tried to access the documents using CSOM they got an error 'Exception calling "ExecuteQuery" with "0" argument(s)" "File Not Found."
The solution in the end was rather manual but very simple, to change the name of the document then delete it via GUI or PowerShell and since it was a small hand full of documents that was what we elected to do. If you have a large number of documents I would recommend calling support and working with them to clean up the documents.