I wanted to resync in machine B an already synchronized folder. I forgot to empty this folder first. Started syncing. A second later I set machine A on read only.
And I’m renamed the folders in machine B. I renamed the folder ‘htdocs’ to ‘htdocs_OLD’ and created a new empty folder ‘htdocs’.
Immediately B sent me the error message: Error on folder folder marker missing
I wanted in B exactly the content of A. It was a fresh new attempt.