Here's the caption attendant to the illustration below:

Figure 4. Example of one echart defect. This is a full screen view. The top view (A) alerts us with the white patches that there are large scale charts available in that region. (B) shows zoomed into that region with multiple zoom-in steps, (C) is the very next scale step in from the view above it, which does show the light. (D) is next zoom in, and now the light is gone from all further zooms. (E) next zoom in. (F) shows slightly different zoom from a different start that does show the light. The presence of the light and which zooms show it depends on where you start from the white region and how you move the screen before the next zoom. But there is no way to watch your vessel approach this reef on a view that actually shows the reef. This is from an iPad app with poor chart presentation. It might look different in computer software or GPS units running these same echarts.

An excellent blog post from David Burch of Starpath, well worth a read:

http://davidburchnavigation.blogspot.com/2014/12/dont-blame-echarts-for-anything.html