OK --to be clear the share is a local filesystem to the server - but I will take tour advice

what is your guess about block-level in this instance?
If a.gz is a toally new file from the one from yesterday ... but the first 70% of the file is identical, will it see it AS identical?

OK - plan B -- I had done the image backup and today I created a bare metal USB drive, so I booted, created a restore plan and started the restore.

At some point the process stopped with the message "restart for failed files" and the additional data that the network resource was not available.

First, the message wasn't clear "restart what?" the PC, reboot the hard drive? Reboot the USB?
I tried the former and it didn't boot, so i tried the latter were, it seems my only option was to start again.

OK that's fine, I started again - but the restore started from the beginning ...

So I have no idea what "start again for-failed-files" meant

What I supposed to have left the original boot and just tried to restart it?