User cannot always scroll to the bottom of the software updater window, last update package(s) inaccessible

[spike speigel]

The user cannot always scroll to the bottom of the software updater window. The scroll bar stops before actually reaching the bottom, and prevents the last listed package or group of packages from being viewed. This seems to happen only sometimes. Not exactly sure what caused the scroll bar hangup one moment and then it functioning fine the next.

Attaching screenshots of the scroll bar working and stuck (movable, but not able to reach the bottom.)

In the initial screenshot the Ubuntu Base package group can be seen partially obscured at the bottom of the list, and the scroll bar is nearly there, but will not move any further to the bottom of the pane. There is also a horizontal scroll bar for some unknown reason, and may be causing the issue.

In the two subsequent screenshots moments later the Ubuntu Base package group is visible and accessible. The horizontal scroll bar is now gone, and may have disappeared while expanding/contracting some package groups.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: update-manager 1:19.04.8
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 nvidia_modeset nvidia
ApportVersion: 2.20.11-0ubuntu15
Architecture: amd64
CurrentDesktop: XFCE
Date: Sat Jan 18 18:20:40 2020
ExecutablePath: /usr/bin/update-manager
InstallationDate: Installed on 2019-03-07 (317 days ago)
InstallationMedia: Xubuntu 18.10 "Cosmic Cuttlefish" - Release amd64 (20181017.2)
InterpreterPath: /usr/bin/python3.7
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=en_US
 PATH=(custom, user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
Python3Details: /usr/bin/python3.7, Python 3.7.6, python3-minimal, 3.7.5-1ubuntu1
PythonDetails: /usr/bin/python2.7, Python 2.7.17, python-minimal, 2.7.17-1
SourcePackage: update-manager
UpgradeStatus: Upgraded to focal on 2020-01-10 (8 days ago)