The second is an almost inconceivable scenario, the new bits match the new signature. I will describe this in more detail later. All other errors are just modifications of these, possibly on larger scales. The correctional software should then simply attempt to write the same file to the server, as if the originator of the file did it. A file is not listed on a majority, but is listed on this server.
Correct behavior is to leave it there.
The likelihood of another file colliding with that signature should be low, AND, there is a possibility that the other writes have not completed yet. This also allows people to use replicas as an alternative to local disks that are not replicated. A deposit is attempted, but the signature does not match the bits. The server should refuse the file with an error. A deposit is attempted, but the signature scheme is not recognized.