The road is like that for miles with some lights, traffic circles, etc... Only warnings in one spot.
I really didn't believe my wife, or thought maybe it was happening a few times when she made a regular trip like getting drive thru coffee and coming right back. But then we ran a bunch of errands all afternoon and got one warning there on the way out, and one warning on the way back.
That’s probably it.
If I were designing a wiper fluid warning, I would use some sort of fluid level sensor and I would denounce it aggressively: the indicator would only light up if the sensor detected a low level for more than a couple seconds. That way traffic circles, bumps, etc would not cause many false positives. I might even couple it to some kind of acceleration sensor so a warning would not turn on during or shortly after any heavy vibration or acceleration.
A long slow bend would cause a prolonged, steady centrifugal force and/or sideways acceleration due to a banked road, which would defeat these mechanisms.
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.
Maybe you found the sweet spot at a certain point in that long, slow bend?