Hi
I had a similar problem only I couldn't get the boot open at all! The "zapper", the button under the steering column, the button and the key above the rear number plate wouldn't work either. There is no mechanical back up to open the boot, everything is electronic and as we all know the rear seat release mechanism is inside the boot so I was stuck. In the end I took my XF to a local (excellent) dealer who got the boot open and found 3 broken wires in the loom. I have opted to have the loom replaced (€60 plus labour) as I do not want to arrive at some distant place and discover that my luggage is trapped in the boot. This is obviously a poor quality/design matter that rests firmly a Jaguar's door. I don't think it's a matter of chafing, my problem arose during a cold spell and I think the wires became brittle and snapped. My XF is only 5 years old with 50000 miles on the clock and is in very good condition. The wiring is obviously not up to the job and should not fail after 5 years of normal use!