This is what I did and it works for me.
If the user types in a valid address that Google Maps can find it will update the map when they click Find on map.
If the user types in an address Google Maps can't find, then the pin will go to an alternate similar address while the address the user typed in stays the same. The user can then drag the pin to where it needs to be. The whole time the address they typed in stays the same.
On the admin backend go to Plugins. Find the Draggable Marker Vantage plugin and click Edit. On the right under Plugin Files click draggable-marker-vantage/draggable-marker.
js.
In the code window go down to line 23 and comment out the below code like I have it.
This will keep it from updating the address when you drop the pin after moving it.
Code:
// function updateAddress(pos){
//
// geocoder.geocode({latLng: pos }, function(responses) {
// if (responses && responses.length > 0) {
// var addr = responses[0].formatted_address;
// jQuery('#listing-address').val(addr);
// }
// });
// }
Go down to line 57 and comment the line like below.
This will prevent the wrong address from being sent back to the address field overwriting what the user types in if Google can't find it.
Code:
//jQuery('#listing-address').val(results[0].formatted_address);
Click the Update File button.
I hope this helps.