This is the hack you do where you create a VHD on a network share and mount that to do a system image backup. It will work the first time, but once you unmount the volume and re-mount it later, it won’t work, with the error message “The version does not support this version”, or something like that. It means that windows backup doesn’t like sparse files, which is what gets created with some combination of SMB and ext4. You can turn off sparse file creation in smb.conf, but then what happens is that the smb client on the windows machine will time out as it’s waiting for the file to get written.
I don’t know of a solution, but I’m not doing these backups on the MBL anymore anyway. Just though I’d let people know.