Could be the boot actuator or the remote fob receiver. Have you tried using the spare key to see if it definitely isn't the main key playing up?
Also you could look at getting a diagnostic check carried out or get an auto electrician to take a look as it could be a broken wire.
Also unsure if it would be relevant but has the car got wet carpets? I ask as the comfort control module is under the carpet passenger footwell. If the footwell gets wet and floods the ccm it can cause all kinds of weird electrical issues.