Hi again, check your Develop Assistant settings. At some point, you've switched to 32-bit output rather than 16-bit. 32-bit will be using a linear colour space, which Apple Photos doesn't interpret correctly, so it's causing the mismatch that you see when passing the document back. Once you switch back to 16-bit and then open a RAW file from Photos, everything should then correct itself (that's my hope, anyway )
If you're not sure where the assistant is, check out this video:
Bear in mind that you might have to re-open the RAW file once you've changed the setting for it to apply (the above video will need an update when I have time!).
nosillacast reacted to James Ritson in Images are VERY dark round tripping from Photos