Your problem is interesting in that this happened with the default markers. I described a similar issue for custom tokens on a blog in February 2012: http://www.gutensite.com/Google-Maps-Custom-Markers-Cut-Off-By-Canvas-Tiles
We had problems with the Google Maps API version 3.8 (newer than a few others that offered solutions here). Custom markers will be disabled, but the default markers will not. We found that this was caused by new canvas tiles, which are used to optimize the display of Google Maps. If you check the elements, you can see that the markers are actually tile layers.
If we disabled "optimized" (see code below), then the markers displayed correctly! So it seems to be related to the optimization code.
var point = new google.maps.Marker({ 'position': position, 'map': this.options.map.construct, 'icon': marker_data.custom_icon, 'title': marker_data.title, 'optimized': false });
I have not confirmed whether this issue has been fixed by Google since or not, or if there is a better solution.
Others suggested that if you parseInt () the width and height of the markers, they solved their problem.
See related article for photos. Stackoverflow will not allow me to include them because I do not have enough reputation points: - \
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