Issue with mute button when using bluetooth headphones?

Anyone else have this issue? Razer Blackwidow Elite keyboard Alienware PC Sony bluetooth headphones. If I press the 'mute' button, the light flickers and sound stutters like it's not quite sure which app it's supposed to be 'muting'. After a short while it then turns volume to zero, so when I 'unmute' by repressing the key, nothing happens and I have to manually use the wheel to restore the volume. This does not happen when using wired speakers - just the Sony bluetooth ones. Can't really work out where this fault would lie - is it an issue with the keyboard, the headphones, or the operating system?