Ive expected an strange error.
After saving and then returning to the main menu, i get an error message.
It is attached as picture below.
When this happens, the last saved savegame is lost.
(Lucky for me that i always have 2 save slots...)

This error does not appear, if i leave the game completely (Quit to desktop instead
of quit to main menu).

My Version: Windows (10 64 Bit)

Linux version?

https://www.gamingonlinux.com/articles/the-rpg-pathfinder-kingmaker-is-out-with-critical-bugs-in-the-linux-version.12635/page=3#comments

There's also already posts here in the forum.

Im playing the Windows Version. (Win 10 - 64 Bit)

In that Linux Forum there are talking about a game crash.
My game is NOT crashing. Only that error appears. When i click on "Close" i can still play.
No freeze, no crash. Only the last saved savegame is not longer available.

The bug reports forum on Steam is plagged with threads talking about this error, no matter if it's for Linux or Windows (or MAC). Well, Windows 10 for what i have read, it seems.

In some cases is exactly the same error as you have, and i find someone who said that "mostly" all the saves deleted are the regular saves, and that using more quick saves a few minutes difference from the regular ones help preserving the games.

Don't trust the regular, normal saves. It seems that quick and auto-saves are not being deleted, so take that in account. I can't verify, though, don't own the game yet and not sure if i will buy it seeing the big quantity of problems the game has, technically and balancing speaking.

Source: a lot of threads! like

https://steamcommunity.com/app/640820/discussions/5/1734339901254361773/
https://steamcommunity.com/app/640820/discussions/5/1734340257880804147/
https://steamcommunity.com/app/640820/discussions/5/1734340257881166064/
https://steamcommunity.com/app/640820/discussions/5/1734340257880871725/ (look at the image with error here)