The RangeSlider value property does not take into account the from value when the stepSize is changed.

RangeSlider {
    from: 10
    to: 100
    second.value: to
    stepSize: 10
    snapMode: RangeSlider.SnapAlways
    first.onValueChanged: console.log("Value is", first.value)
}

Move the slider, the console will print

qml: Value is 10
qml: Value is 19
qml: Value is 28
qml: Value is 37
qml: Value is 46
qml: Value is 55
qml: Value is 64
qml: Value is 73
qml: Value is 82
qml: Value is 91
qml: Value is 100

rather than stubbornly increasing by the set stepSize of 10. If I change from to 0 this works as expected.
The snapMode does not affect this behavior.