all my achievements disappear after I delete one of my game saves. I am 100% sure that I have not reset the achievements. I would be happy to share this save with you to check what happened but, as you can guess, I do not have it anymore
Hello, how did you delete the save? From in-game menu or you deleted a file on disk? If you deleted something on disk, are you sure you deleted just single save file and not whole folder with Factorio user data?
Can you provide factorio-current.log, please?
Are you sure you didn't downgrade your factorio version? If you start the game for example with 0.16.23 and then downgrade to 0.16.22 all achievements are deleted (this should imho be fixed too btw...).