Rear Differential Fluid Leak 2015 X250 XF

I’m looking to buy a last of the X250 XF 3.0 Diesel. I searched through the MoT history of one car and saw that it had an advisory for: "Fluid leak, but not excessive rear differential (8.4.1 (a) (i)) on its first MoT 3 years ago at only 20,000 miles. This advisory is not mentioned again on future MoTs. The car has a full Jaguar service history and has been serviced 3 times at the main dealer since this advisory.

I was just wondering if there is a known problem with the rear differential on the 2015 XF? I understand that there was a problem with the 2009 XF but am I right in assuming this would have been resolved by 2015? Ironically, I owned a 2009 XF and as far as know, it never had any differential problems.

I’d greatly appreciate any advice - I’d imagine that the Jaguar main dealer that supplied and serviced the car from new would have solved the problem (the car has now travelled another 20,000 miles since this MoT advisory 3 years ago) but as you can imagine, seeing this advisory on the car’s first MoT concerns me.