Interesting seam allowance. I was trying to put C3 to C56 on fold and tried several ways. I just couldn’t get it to work. My path started at C56 going clockwise and these images are what I got. Started my path at C3 and it worked perfect. If you don’t succeed try try again.
Just remember that when you select a curve and then a node on a curve, you must select the curve again if you want your curve to continue. However, I see that you seem to have a “cut on fold” or something between C57 and C3, so this is best left straight.
Also, when your pattern gets covered by the seam allowance, it’s often a curve that is selected that is going anti-clockwise. This can easily be corrected in the Options by reversing the direction of the curve. If a node has been skipped, then it can be added later and dragged to the correct position in the Options.
Very well done
I like the way you have tested the edge of the seam allowance. I’ll have to borrow that from you and test them for myself