If the Timeline part of the control is shrunk to a state it doesn't need a scroll bar anymore (by changing PixelLength or VisibleRange) and after that it is enlarged, its size doesn't change, but the ScrollBar values update. Available in LIB version 2016.2.627, it will be also available in the 2016 R3 release.
Yes, the entire control gets 'stuck' in the shrunk state if you zoom out using the PixelLength. The entire EventsPanel can be shrunk to just a few pixels wide, instead of the width of the screen. It remains shrunk until the user changes the window size or scrolls. It makes zooming a very awkward operation.