EDIT:
I've solved the problem. Apparently the drive I was storing "My Documents" got full ( I didn't see any notifications in Windows for some reason...) . I guess the quick saves worked while they were below a certain size on an almost completely full HDD, and failed to properly save once above that, at which point the previous session's saves were the only usable ones.
I really wish the game had the basest common sense to check that before claiming the game was being saved over and over again...


*****

I've been playing for about an hour today, and I wanted to load a quick save I just made - and out of nowhere a save from yesterday loaded! I still have my saves https://i.gyazo.com/7609662cbbb5829a26c94a212ce92a76.png, but the last one that shows up in game is AutoSave_0036.sav https://i.gyazo.com/458306569f05cd56e479dbece00cc71e.png
This makes no sense- I have been loading quick saves quite frequently during my latest play session. What on earth happened? If it was the latest quick save corrupting, the others should still show up! Can it be fixed? Can it be prevented? Thanks!

Quick saves ovewrite previous quick saves, so you only ever have the latest one.
If it is corrupted & can't load, then you have no quick saves.
The reason Autosaves 37, 38, 39 won't load, is there is nothing in them. look at the file sizes.

As to what's causing the problem, could it be your C: drive is full & the temp directory is getting overwritten between saves?

Was the game installed on the 30th & all the previous saves made on the day the game was first installed?

Edit: And are you using Galaxy?

I know quick saves rewrite old ones, but neither any of my autosaves work from that day's play session, or my latest quick save, whereas my quick saves worked that session up to that point when I wanted to reload it and ended up with an autosave a day old loaded.
I have over 20 gigabytes of free space on my drive where the saves and the game is.
I have been playing this installation of the game since I started, and I validated my game files in Galaxy, all was in order.
I'm using Galaxy.

What I don't understand especially is why all of the autosaves corrupted from that latest session, why the quicksave kept working for an hour, and why won't my quicksave work anymore, because apparently it's a valid size...

Thank you for your help. I've solved the problem. Apparently the drive I was storing "My Documents" got full ( I didn't see any notifications in Windows for some reason...) . I guess the quick saves worked while they were below a certain size on an almost completely full HDD, and failed to properly save once above that, at which point the previous session's saves were the only usable ones.
I really wish the game had the basest common sense to check that before claiming the game was being saved over and over again...