XJ Portfolio.2014.Amethyst Black.
I have been lucky with this as well. I would say more than 20times when I was rebuilding the engine. The only issue I had was Amplifier failed which I repaired it by replacing the chip.There's been a lot of talk about letting the system shut down because of a couple of instances of problems with, I believe, facelift X250s. My experience with my X351 (and previously with a pre-facelift X250) is that it is not required to let the system shutdown. I have swapped batteries and disconnected the battery for electrical work in both cars without issue.
My key fob does not look like that, it looks like this...
I have the battery disconnected currently and waiting the 33 mins and will report back, a couple things I noticed when I was removing terminals, there was a periodic faint beep coming from somewhere in the boot, and also there was a loose wire that was not plugged in anywhere and I'm unsure where it should be plugged, attaching an image to showI meant the main car battery not the fob that should be done asap.