i had a similar issue with my M50 last week - while changing the oil I added 6 liters to the car but it wouldn't show more than about halfway between on the dipstick. No Engine Oil Low warning, however.
I added another half liter, oil mark didn't move. I then added the rest of the liter, for a total of 7 liters, and it shot up above the top mark to a certain degree.
Never seen this before with my car, which is normally very happy with 6 liters.