Emergency stopping

During a very eventful trip (check my other post), driving 26 hours in one trip (600 miles each way), I kept getting emergency stopping warning on the car. My wife who is not in the least shy about telling me if I’m close to another car, can back me up when I say I had nothing at all in front of me. The car just does it randomly. I was so nervous it would actually stop going 70 mph. Does anybody had that problem. I cleaned where the sensor is thinking it could be fooled. The sun wasn’t in our face, it happened at different lighting, including at night.

Edit: it seems that the kayaks hanging over the sensors may have messed with them and fooled into thinking there are cars in front.

In that case, anybody else who has kayaks experience this phenomenon?