The default volume for system sounds is set at 50%.
Everytime I change this to 100% using Pavucontrol, it just reverts back to 50% on every login or reboot.
Any ideas?
I think you need to set the correct volume with kmix as this one restores the volume on login.
Thanks leszek, that was the issue.
When I changed the volume in system settings / Applications & system notifications / player settings.
The volume now sticks.