After connecting to a VPN is almost impossible to disconnect:

- the VPN Connection inside the right stripe (click the network icon on the traybar) never show Disconnect button, also after the connection to the VPN the button remains "Connect" (so can't be used to disconnect).

- open Network Connections (Control Panel\Network and Internet\Network Connections), right click the VPN Connection and clicking Connect/Disconnect on the context menu opens the stripe mentioned before.

The only possible solution is to open Network Connections (Control Panel\Network and Internet\Network Connections), right clicking the vpn connection and select Status from the context menu, on the status window click the Disconnect button, this finally works!

Thanks for your efforts finding this possible solution. I will record this issue.