How to handle doubtful signature inquiry affecting promotion and superannuation?

An inquiry was initiated regarding a doubtful signature. The person whose signature is in question has passed away. The competent authority is not satisfied, even though the forensic laboratory couldn’t verify it due to the unavailability of the original signature. My promotion may be denied, and my superannuation is due on 31/12/2023. Kindly guide me on the next course of action.