Possible Causes

WARNING: This page is about a different car, the 2015 Land Rover LR2, 2014 Land Rover LR2, and 2013 Land Rover LR2. However, it is still accessible from the selected car via links, so may be relevant.

Low voltage on right actuator during operation (full clamping force not reached within allowed time)
Right electric park brake actuator incorrectly installed to the vehicle
Right electric park brake actuator circuit, open circuit, high resistance
Right electric park brake actuator internal fault