I had the same problem doing a System Image to a network share. I solved it and it now works after lots of research.. The following fixed my issue:
Turned all these 4 services to Automatic Startup:
-Microsoft Software Shadow Copy Provider
-Volume Shadow Copy
-Windows Backup
-Block Level Backup Engine Service
I also started them if they weren't running.
Used IP address instead of sharename when choosing the location of the network share. Ie type \192.168.0.10\backupfolder rather than \SERVER\backupfolder
Emptied Recycle Bin, closed unnecessary running applications
Checked permissions on server backup folder. Some people recommended adding Everyone and giving them Full Control, but I didn't find this necessary. I checked that the System, Network and Administrators group (which I'm a member of) had Full Control.
Turned Power settings on both machines (local and network) to Never turn off.
Oh I also temporarily turned off File History.
Not sure which of these made the difference but try them all, it may work for you.
Note I did NOT disable my AV (AVG -Active, Defender and Malwarebytes also on system) or Firewall nor did I need to repartition my drives. Also I'm on Windows 10, so saying it doesn't work on Windows 10 is wrong.
Good luck!