Sorry that it didn’t work out.
To clarify things, when I click on my desktop browser the volume up/down-buttons below the rounded control, the volume changes in steps which I have set in the config, except inaccuracy due to roundings “volumio” mentioned in an above post. Same happens when I turn the rotary encoder, or use the mousewheel over the round volume control.
When I use the horizontal slider bar on the bottom of the screen, volume steps are of 5, not 2 as I have configured, also the mousewheel is not active here, this looks like a bug to me.
The behaviour you described, that the volume change is stuck at some point or not reacting at all sometimes, I never experienced by just clicking buttons in my browser or using the horizontal slider, it only happened when using the rotary encoder without capacitors.
When you connect to volumio via ssh, you can trigger on the command line the exact same functions the gui uses:
volumio@volumio:~$ volumio volume plus
volumio@volumio:~$ volumio volume minus
volumio@volumio:~$ volumio volume 35
Have you checked this? Is the volume stuck too this way?
Additionally, if you enable the live log (http://volumio.local/dev), do u see errors when doing volume changes?