Since a few days ago Spotlight (no changes on the system as far as I remember) has been acting up: when I reboot, everything works fine. Then, after a few minutes just some files/folders disappear. Give it a few more minutes and another search and no files/folders can be found. For some reason, Applications, Bookmarks & History, and Notes are always searchable. To make it even more confusing, I left the Mac running for an hour after Spotlight was showing indexing progress, came back to it - and it works. And then in a minute the files again disappear. I tried rebuilding the index, a few times. Ran every command I found on any forum that people said solved their Spotlight indexing issues. Fixed disk permissions. Ran maintenance scripts, etc. etc. I'm running out of ideas. I'd probably assume it has to be hitting an issue after I run a search and that breaks it but I've no idea how to check or confirm that. edit: contacted Apple Support and are resolving the issue with them. It's supposedly a very complex issue and they had to involve engineers.