This isn’t a bug, but rather expected behavior. Save states are not always compatible with newer Citra builds, nor is it recommended to rely solely on them for recording your progress, as they are a lot more unstable than in-game save files. Their recommended usage is within single gaming sessions, not beyond them.
Regardless, if you have important progress saved only on a save state that you can’t load anymore, upload a log file and tell me what save state slot you’re trying to load. I should be able to find the Citra build that can load your save state, after which you can save in-game to continue playing on the latest Citra builds.
I didn’t post a “fix-all” build for save states loading. I merely got that specific user, the specific build to load their specific out of date save state. If you’re getting the same error as the above user, open up your own support topic for it with your own log file. I can help you find what build you need there.