BMW oil pressure red light

Hello,
I have a BMW 330i 2003 clean car and no issue since I bought it. The problem now is the
oil pressure warning light is blinking when the car is idle, especially when I stopped at red
traffic light, but when I move the car, the light goes off. I took it to a maintenance place
where they fix german cars. They did not see the light is on when the car stayed with them
two days. They checked the oil pressure, and it is fine. They also put a new oil pressure
sensor to make sure if is defective. in addition to that, they put a new oil and filter. They
told me light should not be on again, but once I took the car to back home, the light return
on again and I was surprised and dissappinted. I'm planning to take it back to the
maintenance tomorrow, but your suggestion and analysis of this issue are highly
appreciated.

Many thanks and kind regards,