def ChangeCircleRadius( circle, center, radius )
	pts = Array.new
	curve = circle.first.curve
	curve.vertices.each do | vertex |
		vec = vertex.position - center
		vec.length = radius
		pts << center + vec
	end
	curve.move_vertices( pts )
end

I depend on the intersection API for my mechanical drawings. I have observed that intersection (either from the API or the UI) fails to find all intersections if a circle vertex falls on an edge. Moving the circle slightly relative to the edge will fix the problem.

Bob Rice