Thank you for your replyYup, I've had this happen perhaps about half a dozen times in the last 4 years. Luckily every occurrence has been on my drive. I suspect it is triggered by an intense RF field and one of the harmonics of that radio frequency is the same as the one used to operate the tailgate. This is not exactly unexpected as I live next-door to the communications centre for the SAS regiment here in Hereford.