I have all but one achievement.

I first won the perfect knight achievement when I got my last Amadeus Diary, I didn't seem to need to find the final clue to his identity to get the 100%. It did not stick.

I keep unlocking it by restoring my profile and restoring my previous save.

Although I am at 100% already in the game, moving into a new area seems to make the achievement re-pop... However, it never sticks.

Quitting the game and trying to restart usually results in a corrupted save file. I restored my save file many times, tried doing it offline, tried a reinstall, tried unlocking a GFWL achievement in a different game... nothing has forced it to synchronise.

A problem in many games. It got me in GTAIV when I completed the game in less than 30hrs. I hate that these time-expensive achievements so regularly glitch.

If you know of any solution, please let me know. Thanks.