That arc is a reflection of some sort. I had some similar appear in my CDK17 where there had been none the previous times I had used it. Which was quite puzzling as the setup was the same.
I finally tracked it down to the black paint Planewave uses isn't that high quality and it flaked off on the edges of the knife edge baffles.
Touching up the paint, both sides, of these knife edges baffles reduced it greatly and perhaps eliminated it.
The perfect arc is the clue its coming from your scope.
