Jaguar XF problems

The basic answer is that it's not the car, it's the dealer. What you've basically told us is that lots of perfectly good components, including the engine, have been unnecessarily replaced. The problem is probably very simple but the dealer can't find it, and sadly that's not unusual. For any marque.

Your car is a 2012, so well outside the usual 1-3 year fare dealers commonly see. Whilst I've no idea what your problem is, and sadly, as you're in the US and no doubt you have one of the big gas guzzling versions we in the UK rarely buy, our experience is possibly going to be limited, but you need to find a mechanic that actually knows what he's doing. (One over 50 years old ideally).

As an example. A few years back, I had a 3 year old Mercedes E Class. It suddenly developed a judder at tickover. 5 visits to the dealer later, with the usual software updates etc I was told it was perfectly normal and they all do it. They couldn't explain why it hadn't done it for the first 2 1/2 years but that didn't matter. In desperation I took it to an independent specialist who agreed to dig deeper. He called me 3 days later to tell me he'd done all the usual computer and sensor stuff with no success, and finally, gone back to basics and found the fault was actually a plug lead. They replaced the set and it was sweet again.

Another example, my Landrover fuel gauge would randomly drop to 0 on a full tank. 6 dealer visits and 6 "software updates" later, it still did it. In the end I got annoyed (I know something about how cars work) and told them to get a spanner out and replace the tank sender. Reluctantly they agreed. Fault sorted.

Point is, the dealers don't always know best and modern dealer mechanics have very little diagnostic ability these days. if you've got one that's guessing, and yours clearly is, get rid and find another.