I think ‘on value changed’ is only called when you let go of the widget, no?
In any event, a timer is not the way to do this, I think that’s why you’re having a problem. If anything, it would be better to set a bool, saying, ‘an update has taken place’. And then, when they close the widget, you can check the bool and make the update if need be.
The way you have it now, every time they change the value, a new timer is started and the variable ‘slider timer handle’ is overwritten.