Cannot move file issue

[steve.clarke@io]

Hi,
We are experiencing an issue that occurs intermittently and goes on for anything up to two hours before, apparently, fixing itself then continuing to work normally. The FFS log reports this issue as: "Cannot move file. SSH_FX_NO_SUCH_FILE [libssh2_sftp_rename]". We do not understand what this error message means. The Compare/Sync process is moving a file from one location to another and quotes the file it supposedly says does not exist. As I say, this can continue for some time and then suddenly all the failed files are moved and FFS continues on as normal.
Any help regarding what this error means and what to do about it, other than waiting it out, would be appreciated.