grub failed to update, maybe to do with unsigned kernel

[Robin Rounthwaite]

package grub-efi-amd64-signed 1.93.11+2.02-2ubuntu8.10 failed to install/upgrade: installed grub-efi-amd64-signed package post-installation script subprocess returned error exit status 1

ProblemType: Package
DistroRelease: Ubuntu 18.04
Package: grub-efi-amd64-signed 1.93.11+2.02-2ubuntu8.10
Uname: Linux 4.19.18-surface-linux-surface x86_64
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
Date: Wed Feb 6 13:59:27 2019
ErrorMessage: installed grub-efi-amd64-signed package post-installation script subprocess returned error exit status 1
InstallationDate: Installed on 2019-01-30 (7 days ago)
InstallationMedia: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
Python3Details: /usr/bin/python3.6, Python 3.6.7, python3-minimal, 3.6.7-1~18.04
PythonDetails: /usr/bin/python2.7, Python 2.7.15rc1, python-minimal, 2.7.15~rc1-1
RelatedPackageVersions:
 dpkg 1.19.0.5ubuntu2.1
 apt 1.6.8
SourcePackage: grub2-signed
Title: package grub-efi-amd64-signed 1.93.11+2.02-2ubuntu8.10 failed to install/upgrade: installed grub-efi-amd64-signed package post-installation script subprocess returned error exit status 1
UpgradeStatus: No upgrade log present (probably fresh install)