Using pen tool get the random halo effect

the path is blue and the stroke is blue, I can’t tell where I am placing point in the canvas sometimes while drawing.

I see in the preview, some of them has halo inside them and some don’t. I have no idea if I am doing this wrong or something.

I think this is now fixed. However, if you find this issue still happens, it’d be great if you could send me the .mck file you’re working on.