A couple of things to look into to.
- Try zooming the map in. Those two coordinates are less than a mile apart, which means at around zoom level 7 the two coordinates would be rendered in the exact same pixel location and overlapping. When you zoom in closer the pin icons would likely still overlap a bit, until you are zoomed in to about city level.
- Generally you only need to load a module once. Loading the module repeatedly just complicates the code and adds more code for you to debug.
- Make sure you don't have any other code that runs that clears the map between these two calls. Note that loading a module is asynchronous, so a clear method could be called further down in your code but be processed before the module load callback is called.