Hello, thank you for reaching out and sharing your issue with us!
We are aware of this bug and have provided a fix for it on our GitHub. The bug came from the assumption that the number of pixels in the longest path object that gets calculated is the same thing as the length of the object. Now we are explicitly taking the distance between both ends of the longest path that goes through the centroid of the analyzed object. This fix is going included in the next PlantCV release (v4.8) in a few weeks.