You might want to check this review of your Kestrel as it mentions saddle clamp problems and has a video that, sort of, shows the clamp itself. Scroll down to "Saddle Clamp Issues" about a third of the way down and the video is right below it. May be worth it to find a work around if the better parts recommended in the video can't be found.
Kestrel 4000 Review - Seattle Triathlon Coach (tritheos.com) Also the Kestrel website has an archives section that lists seatclamp as being a "Ritchey clamp system" for some of the models.
Kestrel Bicycles | 2016 4000 Shimano Ultegra | Bike Archives