Markers incorrectly changing location on zoom

I have a set of markers being added to a map at zoom level 15. The markers lat and lng are currently set to the 6th decimal place.

When I zoom in or out the marker locations are moving out of their correct position. Do i need to remove and redraw the markers at each zoom level? do I need to increase the accuracy of my coords? this is driving me crazy...

Test page: http://m.uwosh.edu/api/v1.0/map/ click on the yellow icon in the bottom bar.

I'm creating my markers like so:

function createMarker(data, type) 
{
  var posn = new google.m开发者_开发百科aps.LatLng(data.lat,data.lng);
  var title = data.title;
  var image,shadow,shape;
  if (data.typeId === '101') {
      image = new google.maps.MarkerImage('/api/v1.0/map/images/buildings.png',
      // This marker is 20 pixels wide by 32 pixels tall.
      new google.maps.Size(24, 28),
      // The origin for this image is 0,0.
      new google.maps.Point(0,0),
      // The anchor for this image is the base of the flagpole at 0,32.
      new google.maps.Point(0, 28));
    shadow = new google.maps.MarkerImage('/api/v1.0/map/images/shadow-buildings.png',
      // The shadow image is larger in the horizontal dimension
      // while the position and offset are the same as for the main image.
      new google.maps.Size(39, 28),
      new google.maps.Point(0,0),
      new google.maps.Point(0, 28));

  } 
  var markerOptions = {
    position: posn,
    title: title,
    shadow: shadow,
    icon: image
};

var marker = new google.maps.Marker(markerOptions);

    // could add event handler here

    //add marker to array for latter use
    if (type === 'building') {
       buildingMarkers.push(marker);
    }
}

You shouldn't have to add/remove the markers as the markers are placed with the lat/long location.

Perhaps some code may help us figure this out.