A simple reset fixed this... thanks yamaha support.
FYI this is the process.
To reset the unit you will need to make sure you have the unit in standby including zone 2 switched off. Operate the unit from the front panel, start by pressing and holding the straight button while pressing the power button, Advanced Setup will be displayed and you can release the buttons. Using the program arrows navigate to the option Initialize - Cancel. Press the straight button repeatedly to change the option to Initialize - All and turn the unit off again.
Upon turning the unit back on the system memory will have been reset so all speaker settings radio [presets and any customization done will be lost. Test the volume display again to see if this has resolved the problem.