Swift MKMapView Polygon Overlay glitching
<p>In rare occasions, the overlay on my map (small blue dot) gets a weird glare (big blue area on right) (as seen in picture). Sometimes zooming in or out will fix it, but not always. Can't find anything on why this would happen. Is it something to do with how it is rendered?</p>

<p><a href="https://i.stack.imgur.com/ifRdp.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/ifRdp.jpg" alt="enter image description here"></a></p>

<pre><code>func drawLocations(_ loc: CLLocation)
    {
        let center = CLLocationCoordinate2D(latitude: loc.coordinate.latitude, longitude: loc.coordinate.longitude)
        let lat: CLLocationDegrees = center.latitude
        let long: CLLocationDegrees = center.longitude
        var points = [CLLocationCoordinate2DMake(lat,long),CLLocationCoordinate2DMake(lat,long),CLLocationCoordinate2DMake(lat,long),CLLocationCoordinate2DMake(lat,long)]
        let polygon = MKPolygon(coordinates: &amp;points, count: points.count)
        DispatchQueue.main.async(execute: {
            self.mapView.add(polygon)
        })
    }
func mapView(_ mapView: MKMapView!, rendererFor overlay: MKOverlay!) -&gt; MKOverlayRenderer!
    {
        if overlay is MKPolygon
        {
            let polygonView = MKPolygonRenderer(overlay: overlay)
            polygonView.lineWidth = 4
            polygonView.strokeColor = UIColor(red: 30/255.0, green: 12/255.0, blue: 242/255.0, alpha: 0.4)
            return polygonView
        }
        return nil
    }
</code></pre>