RingCentral for Windows, latest version (22.214.171.124474). On a Surface Pro with DPI scaling turned on. Everything is huge, so huge that the window at its smallest size extends well beyond the bottom of the screen, placing many buttons out of reach. Even when I maximize the window it dosen't work well. On the Dial Pad the green call button covers half the bottom row of numbers. You can forget about the settings window, it can't be resized and disappears above and below the screen. I have tried switching scaling to being performed by the Application or System and it does the exact same thing.
Having the same issue on Surface Pro 4. Even if I change the display properties to scale 100% (allowing me to get the maximize/minimize buttons) the app window is huge and cannot be shrunk down using sizing handles.