I originally posted this issue at Microsoft Community ( http://answers.microsoft.com/en-us/windows/forum/windows8_1-files/shadow-copy-snapshot-file-contents-silently/06a5e25b-6607-45eb-81a1-71cfc2b0cce3 )  but I think it might get more attention here.

Historic overview:

One user had problems with Folder Redirection sync resulting in data loss (details are irrelevant) and we had to recover missing data from PC's VSS snapshot of CSC cache (regular VSS snapshot by System Restore).

In short steps:

1. Elevate to SYSTEM with PsExec (CSC folder is heavily protected by ACL so we have to use SYSTEM to access it)
   psexec -i -s -d CMD
2. Get relevant shadow copy with
   vssadmin list shadows
3. Mount shadow copy with
   mklink /d C:\ShadowMount \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy1\
4. Recover data with
   robocopy C:\ShadowMount\Windows\CSC\...\data D:\Backup /E

No errors were seen and a few test files were consistent. About a month goes by and user reported that most of the data was corrupted. We determined that data had been corrupted already during recovery from Shadow Copy.

We have been able to reproduce this on 3 Windows 8.1 systems so far (not tested on 7 yet).

We also tried to over Network provider just in case, but we still see corruption

1. net use vss$=\\?\Globalroot...
2. popd \\localhost\vss$
3. Access data

Symptoms:

Snapshot age seems to be largely irrelevant (corruption in both snapshots taken a month ago and yesterday).

Parts of the file or whole files are filled with NULLs. It seems that NULLs occur at cluster borders (4kB clusters).

It does not matter if file exists on live volume or has been deleted/moved since snapshot.

File is OK on live volume.

For example one text log file (for easy content analysis), size ~244kB analyzed in Hex Editor

1. Beginning of file has 12kB of data (last data char is position 2FFF)
2. After that, only 00 characters (NULL)
3. Data continues at position 3B000 until end of file

ChkDsk /scan shows no errors. The system has been patched up-to-date with WU patches. No LDR hotfixes deployed to my knowledge.

Systems are running regular HDD (so TRIM hasn't cleared up clusters).
Background defragment is enabled.

No VSS errors in Event Log.

The files were very unlikely to be in use (old documents, images, beforementioned old log file) during snapshot.

We're aware that Previous Versions has been dropped in Windows 8, but underlying Shadow Copy technology still exists and should continue to work.

We are considering that this might be a bug in VSS. Shadow copy is not consistent and parts of it are either dropped, overwritten or... something.

Might it be a bug or am I missing something? Should we get a MS support case?
We didn't find any relevant KB articles for Windows 8.1 but found one similar case: http://superuser.com/questions/888383/shadow-copy-recovered-files-contain-lots-of-null-blocks
Windows 7 and previous seem to have had a similar case in the past: https://support.microsoft.com/en-us/kb/2748349

Hi Don,

Volume Shadow Copy does not exist in Windows 8.1. It was removed since Windows 8. A new feature named File history is replaced.

Previous versions UI removed for local volumes

https://msdn.microsoft.com/en-us/library/windows/desktop/hh848072(v=vs.85).aspx

Shadow Copy does exists in Windows 8.1 as it is required functionality for System Restore and consistent backup.

Your link confirms that Previous Versions UI has been removed, but explicitly states that Shadow Copy technology still exists:
"Developers who need to create shadow copies of local volumes can still do so by calling VSS APIs in custom code."

VSS API's and tools still exist, but retrieved data is corrupted.

If your copy file is not corrupted, try this tool ShadowCopy V2.02 https://www.runtime.org/shadow-copy.htm 

If your copy file is not corrupted, try this tool ShadowCopy V2.02 https://www.runtime.org/shadow-copy.htm 

• Marked as answer by Bruce WoodingModerator Wednesday, June 03, 2015 1:00 AM
• Unmarked as answer by Don Zoomik 15 hours 58 minutes ago

If your copy file is not corrupted, try this tool ShadowCopy V2.02 https://www.runtime.org/shadow-copy.htm 

• Marked as answer by Bruce WoodingModerator Wednesday, June 03, 2015 1:00 AM
• Unmarked as answer by Don Zoomik Monday, June 08, 2015 3:22 PM

The issue remains unresolved.

I just created a Microsoft Professional Support incident, let's see what happens...

Hi Don

Thanks for your update. Look forward to receive your good news.

Ok, thanks for your update. It seems the only way is to waiting the hotfix now.

Microsoft Professional Support confirmed the issue (previously unknown by Microsoft). No workarounds but there will very likely be a public hotfix in the future (currently there is no timeline).