Game not saving when I save it

At least half the time when I save my game, it doesn't actually save. It says it did, and the new save reflects the current time, etc. However, when I reload a save because I died or get off the game and reload into it, it puts me back at a previous point in my playthrough rather than at the point I actually saved. It's incredibly frustrating having to constantly replay hours of the game that I JUST completed, and it makes me never want to play the game again. I have tried double saving, only saving at the Lighthouse, all kinds of stuff.

In addition, I've tried to delete old saves to try to prevent them from interfering with my new ones, but once I confirm that I'd like to delete a save, nothing happens. Every save remains.