There is an issue with adding a pin after the zoom scale has been changed.
Simple workaround is to reset the zoom scale to 1.0 before adding the pin.
// Calculate zoomed out position
CGPoint point = CGPointMake(location.x / self.mapView.zoomScale, location.y / self.mapView.zoomScale);
// Zoom to default level
[self.mapView setZoomScale:1.0 animated:YES];
// Focus on correct position
[self.mapView centreOnPoint:point animated:YES];
// Add annotation at new point
... = [NAAnnotation annotationWithPoint:point];
Fixed with the release of v2.0