A XF sport rake given a clean jaguar health check needs a new rear suspension arm after 1600 miles, 50300 miles on clock, is this believable

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Car taken to Stratstone, Sat Nav Reverse camera and audio all went blank. Still has waranty till June 2018, Also two recall jobs to do. They gave it a full health check and found a badly worn rear suspension arm. They gave this car the same health check 1600 miles ago with a clean suspension report. The car is a 2013 facelift model with 50300 on the clock, I just don't believe it. Bill £600. They are also going to charge for the electric fault, not uppedr the waranty,even though after a week they still haven't found the fault. So they say. Probably just a bad earth, Their customer service is very poor. Can't get through to them, but prommis to phone back ,which they don't do.