This was ArriRaw and 16:9 2.8K. 25fps, 180 shutter. But it is also visible in ProRes 3.2K, and with difference fps and shutter. I have not tested it in Open Gate.
It is visible pre grading, and in different software. The images is exported from DaVinci, but the patterns is also visible with ArriRaw Converter.
I have been given feedback on that this is a normal behavior when there is objects clipping in the frame. But if this is a behavior that is normal I would be reassured that this is observd by others shooting with Alexa. In other words that it is not a quality deviation.