As above. My Pro's Pro XP Plus crank was recording 12 lbs when set to 24 out of the box. Regardless of what the documentation claims (factory calibrated) it's likely way off. I started with the Shuttle Express but the support mount holes where drilled too small at the factory (confirmed bad batch) so returned it for the XP Plus. Assembled and tested at factory? I don't think so
Have you calibrated it? It's not too hard, manual has instructions. Loosen locking nut, turn clock or anti clock to increase or decrease then crank fish scale again. I wouldn't use any crank or electronic pull device, even a Wise without checking it against a scale or calibration device first. EDIT: Just looked at your photo again, are you locking the string into the gripper properly before cranking? Silly question but in your picture the string isn't locked in the gripper so thought I'd check.
Another thing you could check is if the brake disc is attached to the crank handle correctly. Remove the screws holding the white cover on, and you should see that the disc has holes for the crank mechanism. Make sure the disc is turning when you turn the handle.
