Hello.

I last played SoC on November 2018 and have all of my saves plus the game installed, since then.
Today I wanted to continue playing but I'm getting the error in subject every time I load a saved game and game crashes.

I'm playing vanilla, tried verifying game files and reinstalling, there's no way to make it work again; only starting a new game works.

Any help?
Thanks

I'll hazard a guess: you installed STALKER Complete or ZRP. ZRP replaces Hunter's sawn-off shotgun with a long-barrelled shotgun for immersion, and STALKER Complete uses ZRP 1.05 R10 for its bug fixes.

You can't use saves made with any mod other than the simplest mods, as they change the game. These changes are stored in the saves. To make your saves work, you would need to reinstall the same mod first.

If you had not said that starting a new game works, I would have said you had a virtual store (AKA shadow copy) issue.