This is usually caused by improper installation or a loose screw. Please check the following:

Check the front edge of the panel
If the front of the armrest panel has come loose, remove the rear screw, detach the panel, align the front edge with the slot, snap it back into place from front to back, then tighten the rear screw.
 
Check the rear screw
If the front edge is secure, inspect the rear screw. Tighten it if it’s loose. If the screw is missing, please contact our support team to request a replacement.