Maybe it's a combination of the "bend" and the "long slow" part.
If you are making a turn the centrifugal force will push the fluid away from the axis of rotation. There is likely a level sensor only on one side of the tank, so the turn might push the fluid away from the sensor enough to trigger a warning.
The sensor likely has a time component to avoid triggering every time you make a turn, but if this bend is long enough, maybe the fluid is displaced long enough that it overcomes that minimum time.
If you are making a turn the centrifugal force will push the fluid away from the axis of rotation. There is likely a level sensor only on one side of the tank, so the turn might push the fluid away from the sensor enough to trigger a warning.
The sensor likely has a time component to avoid triggering every time you make a turn, but if this bend is long enough, maybe the fluid is displaced long enough that it overcomes that minimum time.