So, I was 34 hours into the game and my character died, taking me to the loading screen. It got about 75% of the way through loading and the screen changed to the main menu, except with my character present staring at the floor with the message “load game failed”. This meant that no matter how many further saves I made I would not be able to load them, and was permanently stuck at my last valid save.
It seems that many other people had this problem also, and may of them could not resolve it. Some said that I should restart my console, didn’t work. But another solution put forth was that one should go through each previous save game and delete them until only one remained. It could be the last save made, or one from a while beforehand, so I did that. This fixed it. I can’t say that I understand how, or why, but it did. If anyone on PS4 is having this problem I’d advise trying this before starting a new game, but after trying solutions that would result in deleting save files.