So I contacted sega the other day about the glitched achievments and I got this reply
Thank you for contacting SEGA Europe.
We are sorry to read that you are experiencing an issue with the achievements.
To date, we have not received notification of other users encountering this kind of problem with this gameís achievements.
Most of the time issues with game achievements not being registered are related to a temporary disconnection from Xbox LIVE, even if itís just for a moment, or to exiting the game directly using the guide button, without exiting the game and going back to the Main Menu. If any of these situations have occurred during the game sessions in which you met the conditions to gain the achievements, it is possible that the achievement hasnít been registered correctly into your gamerís profile.
Achievements are stored locally on your profile, but it is possible that they are not correctly synchronised with the Xbox LIVE servers. Probably your gamer profile sees the achievement as already unlocked and thatís why it doesnít update the state of the achievement.
Thanks for the help sega -_-'