Sony Xperia / Android 9 Media volume loss

[TEKNOPUG]

The media volume control has stopped working on my Sony Xperia XZ3. The speaker still works for calls etc but there is no volume for media. If I look at the sound settings, the volume slider for media volume is greyed out and cannot be adjusted (it's not set to "mute" though).

Android is version 9. I haven;t made any recent changes to settings or updates. Just discovered it in this state this morning. Tried restarting etc.

Any ideas other than a full Reset? I'm working remotely and have an RSA app on my phone for network access which would have to be reset also, which would be quite a hassle.