I guess you will already know it, but just in case: a proper input color profile specifically made for your camera model (and if possible for your own camera) is vital if you need accurate colors. But I’m not sure if that’s your problem.
Perhaps you will have to read how to improve your camera support, because as it is stated in camconst.json (where information about your camera is stored) for your 5D MkIV:
// Quality B, some intermediate ISO samples missing, LENR samples missing so White Levels not properly indicated, some aperture scaling missing
And that quality B may give some hint about why RT doesn’t handle perfectly your images. Not sure, but maybe worth giving it a try?