MKPolylineRenderer CGContext drawPath blurry - swift

Question

I'm trying to draw an arrow on a MKPolyline, which is working well by overriding the draw method, however the result is a blurred line. Any clues on why this might be?
It also does not show the arrows when zoomed out (zoomScale < 0.05), and also increases the line width as you zoom out,
Code below:
class ArrowPolylineRenderer: MKPolylineRenderer {
override func applyStrokeProperties(to context: CGContext, atZoomScale zoomScale: MKZoomScale) {
super.applyStrokeProperties(to: context, atZoomScale: zoomScale)
UIGraphicsPushContext(context)
if let ctx = UIGraphicsGetCurrentContext() {
ctx.setLineWidth(self.lineWidth)
}
}
override func draw(_ mapRect: MKMapRect, zoomScale: MKZoomScale, in context: CGContext) {
if self.polyline.pointCount < 2 { return }
let mapPoints = self.polyline.points()
let startPoint = mapPoints[0]
let endPoint = mapPoints[1]
let p = CGMutablePath()
if zoomScale >= 0.05 {
let midPoint = self.point(for: MKMapPoint(x: (startPoint.x + endPoint.x)/2, y: (startPoint.y + endPoint.y)/2))
let originX = endPoint.x - startPoint.x
let originY = endPoint.y - startPoint.y
let bearingR = atan2f(Float(originY), Float(originX))
let p1 = CGPoint(x: midPoint.x - 60 / (zoomScale + 0.5), y: midPoint.y + 80 / (zoomScale + 0.5))
let p2 = CGPoint(x: midPoint.x + 60 / (zoomScale + 0.5), y: midPoint.y)
let p3 = CGPoint(x: midPoint.x - 60 / (zoomScale + 0.5), y: midPoint.y - 80 / (zoomScale + 0.5))
let points = [p1, p2, p3]
let t1 = CGAffineTransform(translationX: midPoint.x, y: midPoint.y)
let t2 = t1.rotated(by: CGFloat(bearingR))
let t3 = t2.translatedBy(x: -midPoint.x, y: -midPoint.y)
p.addLines(between: points, transform: t3)
}
p.addLines(between: [self.point(for: startPoint), self.point(for: endPoint)])
p.closeSubpath()
context.setStrokeColor(UIColor.yellow.cgColor)
context.setLineWidth(5/zoomScale)
context.addPath(p)
context.strokePath()
}
}