Laptop Sound Adjustment not working when screen is Flipped (invert screen against back of keyboard)

Using a DELL Latitude 7390 2-in-1. Sound adjustment works well when using in "normal" laptop position - When the screen is flipped against the back of the keyboard (to use inverted) the sound is no longer able to be adjusted using the Up/Down switches on the side of the laptop (or even the Keyboard volume switches). Can only adjust sound levels via sound slider on the taskbar. This becomes problematic when watching full screen videos.
Any ideas would be appreciated.
Could not find a setting to solve this issue.