Samba cannot register to the domain controller anymore

On 6 October2020 on an Ubuntu 16 system with kernel 4.4.0-187-generic,
by "unattended-updates", python3-urllib3 1.13.1-2ubuntu016.04.3
is updates to python3-urllib3 1.13.1-2ubuntu016.04.4

After this update Samba doesn't work any more.
Registering of the Samba server at the Domain Controller no longer works.

# net ads join -U admsamba
Enter admsamba's password:
Failed to join domain: failed to lookup DC info for domain 'SAMBA-DOMEIN.LOCAL' over rpc: Undetermined error

From the website below I downloaded the former version python3-urllib3 1.13.1-2ubuntu016.04.3'
https://Launchpad.net/ubuntu/xenial/...ython3-urllib3

With dpkg I installed the former/correct version 3 over the new/wrong version 4.

#dpkg -i python3-urllib3_1.13.1-2ubuntu016.04.3_all.deb
dpkg: warning: downgrading python3-urllib3 from 1.13-1-2ubuntu0.16.04.4 to 1.13.1-2ubuntu016.04.3
(Reading database ... 168370 files and directories currently installed.)

The command below shows that the former version 3 is installed and the new version 4
is available.
# apt policy python3-urllib3
python3-urllib3
Installed: 1.13.1-2ubuntu0.16.04.3
Candidate: 1.13.1-2ubuntu0.16.04.4

After the downgrade, it was possible again to register the Samba server at the domain controller.

# net ads join -U admsamba
Enter admsamba's password:
Using short domain name -- SAMBA-DOMAIN
Joined 'system1'to dns domain 'samba-domain.local'

It seems that python3-urllib3 1.13.1-2ubuntu016.04.4 contains a problem.
Maybe the security update is to strict.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: python3-urllib3 1.22-1ubuntu0.18.04.2
ProcVersionSignature: Ubuntu 4.15.0-117.118-generic 4.15.18
Uname: Linux 4.15.0-117-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.18
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Wed Oct 7 15:12:10 2020
InstallationDate: Installed on 2019-08-19 (415 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
PackageArchitecture: all
SourcePackage: python-urllib3
UpgradeStatus: No upgrade log present (probably fresh install)