To anyone else who found this post trying to resolve Unraid + MacOS Sierra 10.12 Time Machine issues, I followed the following steps on the Synology forum and it resolved the issue on both my machines. I'm assuming it will be patched in a future MacOS release.
[*]Mount the time machine volume as AFP volume: In macOS Finder -> CMD+k (use afp://ip.address/share_name)
[*]Go to macOS System Preferences -> Time Machine -> Select Disk, select the volume you just mounted.
[*]Unmount the share you manually mounted
[*]Time Machine will try to log on and will mount the volume again.
[*]After it finishes up checking it will unmount the volume automagically.
