Upgrading to recent version of Juce leads to an automatic value set when double clicking a slider.
This was not the case in previous version and the doc state
This lets you choose whether double-clicking moves the slider to a given position.
By default this is turned off, but it’s handy if you want a double-click to act as a quick way of resetting a slider. Just pass in the value you want it to go to when double-clicked.