reboot, it worked, then it stopped again. 2 days later still stuck on the same amount of photos I am using optimise storage. I wonder if photos are downloaded in full, analysed and replaced with optimized photos.
Also, if you have an iPad, does it do the same thing or are those changes made on one device sync'd so it knows which photos have been done already? 16,000 photos and it's not at 1000 yet over 3-4 days