try the wd /40 spay first ,but they normally need replacement. . . . .they LR call it a motor for some silly reason, but it is in fact a solenoid with contacts inside . . . .bit like a relay i suppose
I had a similar problem with my central locking a few weeks ago. Landrover wanted to charge £65 to put on diagnostic computer. Got the whole thing fixed at a local auto electric garage, total charge £60, and working perfect now. It was a fault within the alarm/ locking system. I would suggest you try a local auto electric garage first.