I tried to find similar issue on your bug forum but without success. My problem is that when opening a raw image in Develop Persona, I get it by the half and it is duplicated. It just only happen when you open the picture as next one after the first one (the first picture is fine). Looks like only happen when you are using of Apple (Core Image RAW), by selecting it on Assistant Manager. The Serif RAW engine looks like working although. I use High Sierra 10.13.5. Is this a known bug? Picture attached.