OP
It’s hard to help in this situation so everyone is falling back on something they can quantify which is your weight. My first thought since it only happened on 2 day would be environmental. Metal doesn’t fatigue one day, get a good night rest and is all better the next. Was it windy, what was the air temp those two days? Could it be that the other posters are right about your weight and you are on the edge of your limits and the 2 days in question there was a breeze at just the right angle that pushed your set up over the edge or your tire pressure happened to change on them days which affected the ride? How about the road surface, could it have affected the ride? You guys didn’t hit the local all you can eat joint the night before and increased the cargo load did you? It could have even been you after driving for 2 days maybe you were just not as smooth with the wheel.