To anyone aiming for all achievements in DDD, you should be aware there's a glitch with the Record Keeper achievement. I have yet to 100% DDD so I haven't had the chance to encounter this yet, but you should know this if you're planning on 100%ing this game.

The bug can prevent the achievement from unlocking and was never patched on PS4, and so it persists in the Xbox One and Steam versions of DDD. The best information I could find is that the bug may occur if you're NOT playing on the first save you ever created. (Source: https://www.speedrun.com/khddd/guides/5szkc )

Basically, make sure you're going for 100% on the FIRST save you ever created. Deleting all of your saves and making a new one will NOT count as your "first" save, it must be the first save you EVER created for DDD on your account.

I do have a theory that deleting your DDD save data AND the KH 2.8 system data in your "Documents/My Games" folder will solve the issue, but I can't find confirmation on this.

Good luck!