Please see test application to reproduce the issue.
In general there are map and slider. Slider's value is bound with map.zoomLevel. Double click on a map changes zoom level in this application. To zoom in use Left Mouse button, and Right mouse button can be used to zoom out.
Try to switch between view modes (street, terrain, satellite) and pan the map.
Slider often stops updating it's value according with map.zoomLevel after several steps.