I have large numbers of files in my Photos from my recently migrated Aperture library that show a crossed out reference icon
indicating that the "referenced file is offline". If I try to access such files I get a dialog asking me to indicate a specific folder to allow Photos access. Sometimes this (tedious) process works, but often it does not, since the specified folder does not exist. This happens even though the referenced file was present in Aperture before migration. What's the user model here; where did my photos go?