I have created a contour plot from a structured data array (x,y,z). Towards y_max, the function shows a root like profile with a steep gradient. Unexpectedly, the contours show strong wiggles in this region which get even worse when using operator "..".
Creating a contour plot with GNUPLOT, the contour lines are perfectly smooth, so I do not think that the data itself has a problem. Package version is asymptote-1.42-3.fc10.x86_64 on Fedora rawhide, but I have not seen a difference on an FC5 system with asymptote-1.30-1.fc5.