... Essentially you created a transition curve which was too gentle for the maths processor in your computer. "Too gentle" means the radius was changing by too little in too long a transition zone. The problem will disappear as soon as you change one of the radii, or shorten the transition zone. Generally when this happens you can split the difference in radii and replace the transition with a fixed radius curve. Often the screen is more alarming, and you can create some startling effects, like this one from Gordon S: 479_260758_150000000.jpg It's difficult for me to prevent, without restricting the necessary functionality. One day I may have a fresh look at the transition maths -- I wrote the transition code many years ago. Once you know about it you can just ignore it. More about it here: topic_1391&forum_id=4 regards, Martin. posted: 4 Dec 2011 15:53 from: Rob Manchester Hi Martin, Thanks for the reply. I tried to reproduce the problem with 0.91 but couldn't so wasn't sure if it related to the ...