This issue might be due to a defect stemming from the threads of the knuckle or the screw hole on the seat.
To identify the root cause, try switching position the knuckles to see if:
- The second knuckle fits both of the screw holes => the first knuckle is defective
- Or the second knuckle only fits one screw hole => the screw hold on the seat is defective
For this problem, please contact us at Help Center page and provide us a video specifying the issue so that we can look into the issue and help you resolve it as soon as possible.