Live CD installer crashed

I tried to install 20.04 (preview image, downloaded 9-Feb-2020) from scratch, under VirtualBox 6.0.16 r135674 (Qt5.6.2). The host system is Windows 10 64bit, 16 GB RAM.

The instance was given 4GB RAM, 110 GB disk.

On the installation, only mention worth thing was, that I selected zfs as file system. Otherwise, everything else was pretty standard (timezone Europe/Helsinki, keyboard Finnish).

The installer crashed after it had asked me the questions, whether I want to install 3rd party utilities etc, and after I had created the user account. After crashing, it popped up screen, where it asked, whether it can report the error.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubiquity 20.04.4
ProcVersionSignature: Ubuntu 5.4.0-9.12-generic 5.4.3
Uname: Linux 5.4.0-9-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu15
Architecture: amd64
CasperVersion: 1.438
CurrentDesktop: ubuntu:GNOME
Date: Sun Feb 9 12:27:04 2020
InstallCmdLine: file=/cdrom/preseed/ubuntu.seed initrd=/casper/initrd quiet splash --- maybe-ubiquity
LiveMediaBuild: Ubuntu 20.04 LTS "Focal Fossa" - Alpha amd64 (20200124)
ProcEnviron:
 LANGUAGE=en_US.UTF-8
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 LC_NUMERIC=C.UTF-8
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)