There seemed to be a common practice to some people to "copy" the precheck (Scripttool.exe and other files) to the local disc of a running Vault Server environment and run it in order to check if there is a problem prior the update on this Server.
However this is not supported!
The precheck is only supported if it is running through the installer process.
Background is that in some occasions the precheck modifies directly the IIS settings to make it compatible with the new version of Vault Server.
The consequence could be that it brings the existing Vault Server offline!
What we would recommend is to run the diagnostic tool from the existing Vault Server installation.
This would also reflect some issues with Vault before the update.