Unable to get rid of spike on bezier path

I'm drawing some simple bezier paths, but I'm finding it impossible to remove the spikes created when the angle between line segments is small:

(Note: The circle is from a separate drawing operation, but I'm trying to make sure the line does not spike past the circle...).

I've tried all kinds of variations of lineCapStyle and lineJoinStyle but nothing seems to work. In addition to what is shown below I have tried using a Miter Join with 'setMiterLimit'.

Here's my line drawing code snip:

CAShapeLayer *myShapeLayer=[CAShapeLayer layer];
UIBezierPath *myPath=[UIBezierPath bezierPath];
[myPath moveToPoint:tmpPoint];
[myPath addLineToPoint:tmpPoint];         
[myPath setLineCapStyle:kCGLineCapRound];
[myPath setLineJoinStyle:kCGLineJoinRound];

myShapeLayer.path=[myPath CGPath];
myShapeLayer.strokeColor = [[UIColor yellowColor] CGColor];
myShapeLayer.fillColor = [[UIColor clearColor] CGColor];
myShapeLayer.lineWidth = 3.0;

Just in case - here's the Miter code I've used, varying the value rom 0.0 to 100.0 - all with no effect:

[myPath setLineCapStyle:kCGLineCapRound];
[myPath setLineJoinStyle:kCGLineJoinMiter];
[myPath setMiterLimit:1.0];