Hello,
Your construction lines are a little out of square (Align is your friend), also try moving the egg shaped seam to the midpoint of a larger face.Those construction lines have a crazy amount of points, for clarity I rebuilt and aligned, and it chamfered fine, even with or without straight edges enabled. I have some time for a video if needed.
![](get_attachment.php?webtag=MOI&hash=11a32bf3374f74f49958ab4da6a55730&filename=chamfer.png)
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