Interesting but I have a similar problem exporting QT files (4K or 1080 ProRes) for my clients to edit. The images look fabulous in Resolve, but washed out when viewed as .mov QT. I later checked the QT files in Resolve and they looked exactly as I graded them. Blackmagic gave me an unsatisfactory answer so I've counted on client to respond if there is a problem. So far none. I will go thru workflow videos and see what I come up with.