I am having this exact same problem and I agree it is frustrating. It is happening on my iPhone 6, but not my iPad. Yes, the only solution that seems to work is re-download the photos again. When it works, it works well, but when it doesn't, it is very frustrating. Try Google Photos. At this point, it is a better service than Apple Photos. Never had an issue with it and it is faster. Hopefully with IOS 9, they will improve the services they have and fix some of the obvious issues.
06-25-2015 06:09 PM