Ubuntu 20.04 desktop installation crashes

[Irina Belova]

I choose manual modification for disk partitions ("Something else" button) and got installation crash.
Root (/) - on /dev/sda2, Var (/var) - on lvm.

Last messages from /var/log/syslog:

Nov 28 03:56:02 ubuntu ubiquity[6069]: Reverting lockdown of the desktop environment.
Nov 28 03:56:04 ubuntu /install.py: Exception during installation:
Nov 28 03:56:04 ubuntu /install.py: Traceback (most recent call last):
Nov 28 03:56:04 ubuntu /install.py: File "/usr/share/ubiquity/install.py", line 764, in <module>
Nov 28 03:56:04 ubuntu /install.py: install.run()
Nov 28 03:56:04 ubuntu /install.py: File "/usr/share/ubiquity/install.py", line 135, in run
Nov 28 03:56:04 ubuntu /install.py: self.copy_all()
Nov 28 03:56:04 ubuntu /install.py: File "/usr/share/ubiquity/install.py", line 512, in copy_all
Nov 28 03:56:04 ubuntu /install.py: self.db.progress('SET', 10 + copy_progress)
Nov 28 03:56:04 ubuntu /install.py: File "/usr/lib/python3/dist-packages/debconf.py", line 83, in <lambda>
Nov 28 03:56:04 ubuntu /install.py: lambda *args, **kw: self.command(command, *args, **kw))
Nov 28 03:56:04 ubuntu /install.py: File "/usr/lib/python3/dist-packages/debconf.py", line 88, in command
Nov 28 03:56:04 ubuntu /install.py: self.write.flush()
Nov 28 03:56:04 ubuntu /install.py: BrokenPipeError: [Errno 32] Broken pipe
Nov 28 03:56:04 ubuntu /install.py:

Ubuntu version:
# lsb_release -rd
Description: Ubuntu 20.04.1 LTS
Release: 20.04

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubiquity 20.04.15.2
ProcVersionSignature: Ubuntu 5.4.0-42.46-generic 5.4.44
Uname: Linux 5.4.0-42-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu27.4
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.445.1
Date: Sat Nov 28 08:54:50 2020
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed maybe-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)