(version 1.15.0.8 wouldn't let me select this in the version drop down.) Attached is an image from the RTX demo. If you zoom in on the bee in the background you will see trails behind it. This effect is seen on any moving object at the edge of the render zone in this demo, and was first seen by myself as a horse was moving past but I was too slow on the screen capture. It seems to be at the edge of my render zone and i believe the trails are caused by the ray tracing features.