pk-client-error-quarl could not get lock when selecting driver from synaptic

Steps to reproduce (Ubuntu 20.04, synaptic 0.84.6ubuntu5, software-properties-gtk 0.98.9)
1. Open synaptic
2. click in "parameters" menu, then "repositories". This will open a "Software and update" window
3. click on "additional drivers" tab
4. select a new driver (example : I have nvidia 435 installed, I select nvidia 440)
5. click apply

Expected behaviour : the selected driver is installed

Actual behaviour: you get an error window with message:
"pk-client-error-quark: E: could not get lock /var/lib/dpkg/lock-front-end.
It is held by process 9246 (synaptic)"

Workaround: launch "software update" directly without synaptic

I understand that synaptic must be closed in order to let another software updating process operate. But this software update has been initiated from synaptic and I cannot close synaptic when software update is opened. It is opened like a modal window...

Ithink either this feature should be removed from synaptic or avtrick must be found to have it releasing the lock as long as the "software update" window it has triggered is opened; or maybe synaptic and software-update-gtk could share the lock in this situation ? For now it is impossible to install additional driver if you launched it from synaptic.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: software-properties-gtk 0.98.9
ProcVersionSignature: Ubuntu 5.4.0-29.33-generic 5.4.30
Uname: Linux 5.4.0-29-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.11-0ubuntu27
Architecture: amd64
CasperMD5CheckResult: skip
Date: Thu May 14 11:34:44 2020
ExecutablePath: /usr/bin/software-properties-gtk
InstallationDate: Installed on 2020-05-12 (1 days ago)
InstallationMedia: Ubuntu 19.10 "Eoan Ermine" - Release amd64 (20191017)
InterpreterPath: /usr/bin/python3.8
PackageArchitecture: all
ProcEnviron:
 SHELL=/bin/bash
 LANG=fr_FR.UTF-8
 PATH=(custom, no user)
Python3Details: /usr/bin/python3.8, Python 3.8.2, python3-minimal, 3.8.2-0ubuntu2
PythonDetails: N/A
SourcePackage: software-properties
UpgradeStatus: Upgraded to focal on 2020-05-12 (1 days ago)