2018 X2 2.0d with the Aisin 8sp at 27 thousand miles i was getting similar symptoms to the OP, BMW say sealed for life but Aisin say ATF change every 30 thousand, mine would change down harshly and bang into reverse, up shifts were fine though, a pressure flush is not recommended because of the risk of dislodging one or more of the many seals, so 3 flushes seem to be the norm, another issue was trying to get the spec for the ATF as Aisin call it a World ATF or similar, but it's very expensive to buy in one litre containers, i finally found that MANNOL 20L GM DEXRON VI 6 is the right spec, [BMW says its ATF 7 which does not exist] as shown i bought 20l and did 5 flushes which left the ATF in the box spotless, the old ATF was black and so bad i thought i had opened the wrong drain plug ! and i must admit i was very worried at the colour, anyway after following the correct procedures for temp and level etc i found my gearbox transformed, i am lucky enough to have to good diagnostic equipment and performed a gearbox learning reset, now the gear changes are barely perceptible up or down gear changes and reverse is so smooth i only know its engaged because the reverse camera comes, all in it took maybe an hour and half so well worth it, the only things replaced were the 2 o rings from the level plug and drain plug, there are no filters in these gearbox's. hopefully this will be of some help to someone........B
