Guys,
After barely 2 months my X5 has reverted back to the same problem mentioned in this thread. To recap, I thought the problem was solved by replacing the oil sensor. This was good for barely two months as I have encountered the same error messages again....
1) STOP: Engine Oil Pressure Level ???? ( during stationary D gear)
2) Check oil Level ( when I switch off engine)
X5 is going to the shop tomorrow for a check up......