If your save files are routinely corrupting, then something is very wrong because that is not normal behaviour. There are a few ways to corrupt save files:
- force-quitting the game or shutting the console off while it’s saving
- losing your internet connection during an on-line co-op session
- local power glitches affecting your console during a save
- file system corruption on your hard drive
- impending hard disk failure (increasing frequency of read-write errors)
On the first one: any time you pass a New-U, Fast Travel station, or a map transition will trigger an auto-save, so watch out for those if you’re in a hurry to quit or sleep the game.
On the first two: if you suspect this might have just happened (or see evidence of it in-game), you’ll want to make sure the corrupted save doesn’t get backed up by PS cloud sync - if you’re quick, disconnecting from the internet, erasing the corrupt file, then reconnecting to download the cloud save might restore at least some of your progress.
On the last two: if you have had your PS4 for a while, use it a lot, and have never done so before, it may be worth doing a factory reset then re-installing your profile etc. - this would clear up any lingering file system chaos.
One final thing: the game does create a back-up of your save file which it will attempt to use if it detects that the original gets corrupted. However, it only seems to do this when you switch character or switch mode via “Character Select”. The backup can actually be significantly older than the primary save. It’s worth cycling through your saves periodically just to force these backups to a more recent copy of your save files.
That, and making your own backups, should help keep you sane and making progress.