Installer for 18.10 crashes at installing Grub2

[sm8ps]

Have been trying to install 18.10-budgie on an Acer Spin 111-C32 (EFI-system). Having Grub2 installed in the PBR of the boot-partition makes the installer crash. Translated error message: "grub-efi-adm64-signed could not be installed into /target. Installed system will not boot without Grub-Bootloader."
When selecting to install Grub into the MBR of sda, it will simply hang forever. I have been trying for hours now and am about to give up.

ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: ubiquity 18.10.12
ProcVersionSignature: Ubuntu 4.18.0-10.11-generic 4.18.12
Uname: Linux 4.18.0-10-generic x86_64
ApportVersion: 2.20.10-0ubuntu13
Architecture: amd64
CasperVersion: 1.399
Date: Sat Dec 29 16:01:03 2018
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu-budgie.seed boot=casper quiet splash ---
LiveMediaBuild: Ubuntu-Budgie 18.10 "Cosmic Cuttlefish" - Release amd64 (20181017.2)
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)