Can an eSignature be removed from a Vault Document once it is applied?
There is no way to remove an eSignature on a Document once it is applied.
The workaround is to create a new Minor Version of the affected Document. Send the new version of the Document through the Approval process so that the eSignature can be applied properly to the new Document Version.
Vault Document Lifecycle Documentation: Configuring Document Lifecycles to Manifest eSignatures