Tooltips don't disappear on changing workspace

If you hover the mouse pointer over something with a tooltip (popup help message), such as the lock icon in the Firefox URL bar, then the tooltip appears. If you then switch workspace using a keypress (I use ctrl-cursor keys), the tooltip stays and covers whatever is displayed in the new workspace. The tooltip only disappears when you move the mouse pointer over it.

ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: unity 7.5.0+19.10.20190924-0ubuntu1
ProcVersionSignature: Ubuntu 5.3.0-23.25-generic 5.3.7
Uname: Linux 5.3.0-23-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
.tmp.unity_support_test.0:

ApportVersion: 2.20.11-0ubuntu8.2
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: compiz
CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0'
CompositorUnredirectFSW: true
CurrentDesktop: Unity:Unity7:ubuntu
Date: Mon Dec 2 10:21:57 2019
DistUpgraded: 2019-10-04 12:01:19,205 DEBUG Running PostInstallScript: './xorg_fix_proprietary.py'
DistroCodename: eoan
DistroVariant: ubuntu
DkmsStatus:
 exfat, 2.2.0-3arter97-0~201910290835~ubuntu19.10.1, 5.3.0-19-generic, x86_64: installed
 exfat, 2.2.0-3arter97-0~201910290835~ubuntu19.10.1, 5.3.0-22-generic, x86_64: installed
 exfat, 2.2.0-3arter97-0~201910290835~ubuntu19.10.1, 5.3.0-23-generic, x86_64: installed
DpkgLog:

GraphicsCard:
 Intel Corporation HD Graphics 620 [8086:5916] (rev 02) (prog-if 00 [VGA controller])
   Subsystem: Lenovo HD Graphics 620 [17aa:224b]
InstallationDate: Installed on 2017-08-16 (837 days ago)
InstallationMedia: Ubuntu 17.04 "Zesty Zapus" - Release amd64 (20170412)
Lsusb:
 Bus 002 Device 002: ID 0bda:0316 Realtek Semiconductor Corp. USB3.0-CRW
 Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
 Bus 001 Device 003: ID 5986:111c Acer, Inc Integrated Camera
 Bus 001 Device 002: ID 8087:0a2b Intel Corp.
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
MachineType: LENOVO 20HFCTO1WW
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.3.0-23-generic root=UUID=c023de63-612b-4367-874e-b3c987874f56 ro quiet splash vt.handoff=7
SourcePackage: unity
UpgradeStatus: Upgraded to eoan on 2019-10-04 (58 days ago)
dmi.bios.date: 08/30/2019
dmi.bios.vendor: LENOVO
dmi.bios.version: N1WET56W (1.35 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20HFCTO1WW
dmi.board.vendor: LENOVO
dmi.board.version: Not Defined
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.modalias: dmi:bvnLENOVO:bvrN1WET56W(1.35):bd08/30/2019:svnLENOVO:pn20HFCTO1WW:pvrThinkPadT470s:rvnLENOVO:rn20HFCTO1WW:rvrNotDefined:cvnLENOVO:ct10:cvrNone:
dmi.product.family: ThinkPad T470s
dmi.product.name: 20HFCTO1WW
dmi.product.sku: LENOVO_MT_20HF_BU_Think_FM_ThinkPad T470s
dmi.product.version: ThinkPad T470s
dmi.sys.vendor: LENOVO
version.compiz: compiz 1:0.9.14.0+19.10.20190918-0ubuntu1
version.libdrm2: libdrm2 2.4.99-1ubuntu1
version.libgl1-mesa-dri: libgl1-mesa-dri 19.2.1-1ubuntu1
version.libgl1-mesa-glx: libgl1-mesa-glx 19.2.1-1ubuntu1
version.xserver-xorg-core: xserver-xorg-core 2:1.20.5+git20191008-0ubuntu1
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati N/A
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20190815-1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau N/A
xserver.bootTime: Tue Oct 10 16:17:44 2017
xserver.configfile: default
xserver.errors:
 Failed to load module "fbdev" (module does not exist, 0)
 Failed to load module "vesa" (module does not exist, 0)
 Failed to load module "fbdev" (module does not exist, 0)
 Failed to load module "vesa" (module does not exist, 0)
xserver.logfile: /var/log/Xorg.0.log
xserver.version: 2:1.19.3-1ubuntu1.1
xserver.video_driver: modeset