Mercedes 2013 GL 350Cdi Tailgate Actuator and Close Button Issue

I have a Mercedes 2013 GL 350Cdi, the tailgate opens but closes immediately as it appears that the actuator does not lock the tailgate in the open position, I have found that if I hold the tailgate open and press the close button the tailgate does not respond all the time, occasionally I can feel the actuator trying to close the tailgate so it is possible that the issue may be with the close button
AI: Have there been any recent repairs or modifications to the tailgate or its components?
No modifications to the tailgate
AI: Have you checked for any error codes or performed diagnostic tests related to the tailgate issue?
No error codes are given