I've encountered a problem with the Google Maps API, specifically with the KML layers on my Surfy Survey map. The KML-enhanced tiles occasionally fail to load and default back to the normal tiles. This produces a map that shows part of a heatmap, as the two images below illustrate. This behavior is non-deterministic.

Partial tile display of KML layer

Correct tile display of KML layer, created by just refreshing the page

This was tested under Windows 7 in:
Chrome 16.0.912.63
Firefox 8.0
Internet Explorer 9.0.4

Google's tile server seems to fall back to the normal tiles for some but not all tiles, which means that the KML layer is only partially rendered. It would be better if
1. the tile server just delayed the request
2. if the tile server is too busy to resolve the request in a reasonable time, it should return an error
Either way we should end up with a map that features no KML-enhanced tiles, or all the KML-enhanced tiles, but not some of the KML-enhanced tiles!

gmap-kml-tiles-partial.jpg192.76 KB
gmap-kml-tiles-complete.jpg191.75 KB