I'm writing to a QNAP NAS via CFIS. It accepts 100MB/s.
This regards to a file server having 5 disks. A few weeks ago this 100MB/s rate was shared between those this. Since some are smaller they completed sooner and after a while I had this 100MB/s only for the bigger disk (2TB).So it finished on time.
But now, for some reason, transfer rate is always ~20MB/s for all the time.

I get this error:
"Additional Details: 03/11/2019 20:31:59 :: Processing SRVFSS02 Error: Invalid Signature.
Failed to write data to the file [\NASBAK01\Backups\BCK_FS\BCK_FSD2019-11-03T203159_97CD.vbk].
Failed to download disk.
Reconnectable protocol device was closed.
Failed to upload disk.
Agent failed to process method {DataTransfer.SyncDisk}."
I know permitions/authorizations are ok.
Furthermore, I tried to perform an incremental backup in order to have any kind of backup but its seems I cannot force the incremental. Even if I unselect all the "full" options it keeps trying to perform the full...
BR
Paulo Balau