Thanks for your reply. I checked the strands and you were right, some of them appear to be stretched.
I’m not sure when or how that happened. I’ve been using the Move tool to manipulate the shape, setting the Preserve Length parameter to 100, as many tutorials suggest. Usually, it works fine, but something must have gone wrong in the process. I also use some of the Grooming tools, but I prefer to use Move to have more precise control. Now I’m not sure anymore if that works well.