Ok that is known as the current time indicator and by default, dragging in the Time Slider updates only the active view.
this may or may not be the problem but try setting it to all views.
All views can be set to update by changing Playback settings to Update View All in the Timeline Preferences under Window > Settings/Preferences > Preferences and select Timeline in the Categories.

Other than that I don't know of a way to switch the indicator on or off.

Ok after doing some research in the net it seems it might be a video graphics driver issue and updating your driver or trying an alternative driver might fix it.