Hi Arnaud, Ed,
I think we have three problems here, one of which - as Ed has pointed out - is easily remedied by doing a browser refresh in the page: F5 to do a “shallow” refresh, or Ctrl+F5 to do a “deep” refresh.
The other problems have to do with how Google maps handles overlays which are superimposed on each other. Overlays are like transparent foils which can display objects, rectangles, markers, etc.; these overlays are placed in various map panes, like the stacked panes of glass in double- or triple-glazed windows, each of which occupies a definite level in “z-space”, or vertical stacking.
The problem comes when there are many such stacked foils or panes, each showing different and overlapping objects: when the mouse hovers over objects occupying the same x-y position, but different vertical (z) stacking position, and if these objects have defined mouse-events (i.e. show a small info-box on mouse-hover), then google maps is not quite sure which of the objects should take precedence, and hence does not know which of the events to fire.
So, it can happen that, instead of a summit marker firing a mouse-over event, an overlying “nearby region” mouse-over event gets fired instead. Which would mean that, instead of the summit info-box showing, the nearby region info-box is fired instead. Which can be confusing to the user.
Thankfully, there’s a simple remedy - turn off everything you don’t need when examining areas in close detail. So, when zoomed in, as Ed says, it’s best to turn off the nearby regions, which are only useful anyway when you’re zoomed out to the region or country level.