I Have a 2014 XJL exactly same happened to me My 3Ltr engine has done 60k miles. Had it diagnosed by Jaguar specialist and they have pinpointed the Cam shaft as a known fault on the 3Ltr engines also fitted in Range Rovers. As the cam shaft & shells etc cannot be bought from Jaguar they are reluctant to do the re-build & sujest a replacement New engine from Jaguar or replacement re-built engine from Jaguar. This is a massive cost. Not sure if to stick or twist?