Rendering and image quality in MATLAB figures

Question

I have a contour plot and I am using the current rendering:

set(gcf, 'renderer', 'zbuffer');

but it is giving me this thick red line in the plot and I don't know how to get rid of it. I tried switching to:

set(gcf, 'renderer', 'opengl');

but the quality is poor and I really need to have high quality images. Any suggestions?