Bad Sensor or? One lens side progressively worse dust like noise

So.. recording at a venue in 360 mode.. when the video facing the audience section progressively got worse with a dust like grainyness. As you can see from Picture one vs Second Picture below. (lighting conditions did not change). Lenses were clean..no sust..lol. I also put a split picture (third below) to show the one lens side doesnt do this, but the other does. What could cause this issue? Bad sensor? LED lights? It did'nt do this on the other lens.