I purchased a 2015 LR4 mid last year and the dealer carried out several repairs such as broken sun roof etc. We noticed a faint burping sound several times while driving the car and the dealers mechanic claimed they couldn’t get it to do it. The car had 81,000 miles on it and when we received the gas tank was full. After the first Long drive we went to fill up the tank and had the same problem as you. The dealer quoted $2,000 to fix it which I rejected, they said the whole filling tube needed replacing. I had used another group to check the car over for and their LR specialist said it was the filter at the bottom of the fill tube & it required removing the tank to replace. Not having facilities I had them do it for the quoted price of $700, no issues since.