This article describes that cause and possible solutions for the error STC failure occurred mid transfer. stcx.SnapshotError: Snapshot returned error code -87 for STC.
- The error code -87 is an official Microsoft System Error Code for "The parameter is incorrect."
- Third-party VSS-aware applications can block access to the Windows VSS writers, and cause this error.
If you have not done so already, follow the preliminary steps in the Start Here article.
- Make sure that any incompatible VSS-aware applications are not running on the protected server.
- The following backup services are specifically known by Datto to cause Error Code -87 to populate:
- Backup Agent
- Backup Extender
- Backup Updater
If these services are running on the production machine, disable them to prevent future conflicts.