I've tried this on an empty project on Unity 2019.4.0 using this repo and the bitbucket repo
Steps to replicate:
- Import the package into an empty scene
- Add a range slider to the scene
- Hit play
- Make the range slider take up the left quarter of the slider(low at 0, high at 25%)
- Click anywhere between the 25 and 100% area(click at the 75% mark, for example), and drag
- The range slider will move to that area, but the size will also increase along with it