If I acknowledge that the crossfaders have changed from their default then the warning should give me back the slider in its' altered state. BTW even though the GUI won't let me use the slider my controller will.
DJ pro automatically changes the crossfader assignment to use with the Spotify matching songs feature. (Left matches songs on deck 1, right... deck 2) Although the feature is attractive I prefer my crossfader as originally designed. There should be a way to toggle this behavior. It’s really annoying to not have my crossfader available when needed.