Vino server stops when connecting to VPN after upgrade to 20.04

After I upgraded from 18.04 to 20.04, whenever I am making a connection to a VPN server (using Network Manager), vino-server will stop when the VPN connection is established.

This did not happen in 18.04 before the upgrade.

syslog show the following when I connect to VPN

10:02:00 systemd: Stopped Vino VNC server.
10:02:00 systemd: Stopped Vino VNC server.
10:02:00 systemd: vino-server.service: Succeeded.
10:02:00 systemd: Stopping Vino VNC server...
10:02:00 NetworkManager: <info> [1601712120.6080] device (tun0): Activation: successful, device activated.
10:02:00 NetworkManager: <info> [1601712120.6080] device (tun0): Activation: successful, device activated.
10:02:00 NetworkManager: <info> [1601712120.6065] device (tun0): state change: secondaries -> activated (reason 'none', sys-iface-state: 'external')
10:02:00 NetworkManager: <info> [1601712120.6059] device (tun0): state change: ip-check -> secondaries (reason 'none', sys-iface-state: 'external')
10:02:00 NetworkManager: <info> [1601712120.6030] policy: set 'CH-Zurich-zur-c04' (tun0) as default for IPv4 routing and DNS
10:02:00 systemd: Started Network Manager Script Dispatcher Service.
10:02:00 dbus-daemon: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
10:02:00 NetworkManager: <info> [1601712120.5706] device (tun0): state change: ip-config -> ip-check (reason 'none', sys-iface-state: 'external')
10:02:00 systemd: Starting Network Manager Script Dispatcher Service...
10:02:00 NetworkManager: <info> [1601712120.5442] device (tun0): state change: unmanaged -> unavailable (reason 'connection-assumed', sys-iface-state: 'external')
10:02:00 dbus-daemon: [system] Activating via systemd: service name='org.freedesktop.nm_dispatcher' unit='dbus-org.freedesktop.nm-dispatcher.service' requested by ':1.12' (uid=0 pid=817 comm="/usr/sbin/NetworkManager --no-daemon " label="unconfined")
10:02:00 NetworkManager: <info> [1601712120.5428] vpn-connection[0x55c9c0868150,7eaf9e98-1048-4bb3-96ee-5c1dcf4e9b5a,"CH-Zurich-zur-c04",4:(tun0)]: VPN connection: (IP Config Get) complete
10:02:00 openvpn: Initialization Sequence Completed
10:02:00 NetworkManager: <info> [1601712120.5307] vpn-connection[0x55c9c0868150,7eaf9e98-1048-4bb3-96ee-5c1dcf4e9b5a,"CH-Zurich-zur-c04",4:(tun0)]: VPN plugin: state changed: started (4)
10:02:00 openvpn: UID set to nm-openvpn
10:02:00 NetworkManager: <info> [1601712120.5297] vpn-connection[0x55c9c0868150,7eaf9e98-1048-4bb3-96ee-5c1dcf4e9b5a,"CH-Zurich-zur-c04",4:(tun0)]: Data: Internal Point-to-Point Address: 172.21.24.45
10:02:00 openvpn: GID set to nm-openvpn
10:02:00 NetworkManager: <info> [1601712120.5202] vpn-connection[0x55c9c0868150,7eaf9e98-1048-4bb3-96ee-5c1dcf4e9b5a,"CH-Zurich-zur-c04",0]: VPN connection: (IP Config Get) reply received.
10:02:00 openvpn: /usr/lib/NetworkManager/nm-openvpn-service-openvpn-helper --debug 0 2287 --bus-name org.freedesktop.NetworkManager.openvpn.Connection_2 --tun -- tun0 1500 1553 172.21.24.45 255.255.254.0 init
10:02:00 systemd-udevd: ethtool: autonegotiation is unset or enabled, the speed and duplex are not writable.
10:02:00 openvpn: TUN/TAP device tun0 opened
10:01:58 NetworkManager: <info> [1601712118.4499] vpn-connection[0x55c9c0868150,7eaf9e98-1048-4bb3-96ee-5c1dcf4e9b5a,"CH-Zurich-zur-c04",0]: VPN connection: (ConnectInteractive) reply received
10:01:54 gnome-shell: ../clutter/clutter/clutter-actor.c:10556: The clutter_actor_set_allocation() function can only be called from within the implementation of the ClutterActor::allocate() virtual function.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubuntu-release-upgrader-core 1:20.04.25
ProcVersionSignature: Ubuntu 5.4.0-48.52-generic 5.4.60
Uname: Linux 5.4.0-48-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.9
Architecture: amd64
CasperMD5CheckResult: skip
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Sat Oct 3 10:08:27 2020
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
Symptom: release-upgrade
UpgradeStatus: Upgraded to focal on 2020-09-29 (3 days ago)
VarLogDistupgradeTermlog: