RangeSlider showing blank labels once in a while

I'm having an issue while trying to display labels in my RangeSlider.

The problem is the following:

This is my code for the slider:

RangeSlider(
  min: 0,
  max: 5000000,
  labels: RangeLabels(
    'R\$ ${rangeValue.start.round()}',
    'R\$ ${rangeValue.end.round()}',
  ),
  values: rangeValue,
  inactiveColor: Colors.black54,
  activeColor: Colors.black,
  onChanged: (v) {
    setState(() {
      rangeValue = v;
    });
  },
),

And this is the code to show the labels (It's on a theme in MaterialApp in my main file):

sliderTheme: SliderThemeData(
  showValueIndicator: ShowValueIndicator.always,
),