We are facing this issue on our product that customizes GMaps and i was able to reproduce it in gmaps samples:
To reproduce:
1. zoom in a bit so we can move the marker far away from it's location without leaving the globe.
2. click and drag the marker to any other place but it must navigate the map for a bit, by dragging it to the edge of the map.
After some seconds (3 or 5) the marker disappears.
How could I open an issue to Gmaps?