achievements glitched?

i got the crimson map pack day 1 with being a LE owner and i went into matchmaking with a friend splitscreen and first game we played was shatter i believe? with the mantis. i hopped into ours and made our way to the enemies mantis i destroy it with our mantis and get the “pump yer brakes” achievement

then after about 2-3 hours of playing and getting 6/8 of other dlc achievements i notice it still says i need 2 more achievements which i should only need 1 which is the 20 turret kills.

i look at my achievement list and says i never got pump yer brakes achievement and is locked so i was initially like “ok thats weird, thats an easy achievement ill just do it again” well nope i played 2 more games got a board on their mantis and plasma sticky to destroy it then another time i used rockets to destroy it and nothing no achievement.

so is it glitched or something for me now or anyone having same problem? 3 of my friends got the achievement first time boarding/sticking mantis

it’s not just achievements that are glitched. I started a round on the new crimson map and was given the challenges for the day completed while only making a single kill

Tried recovering your gamertag? could be a sync issue

just tried recovering my gamertag and nothing , pretty annoying to know ill be missing 1 achievement even though i should technically have it, nothing game breaking but just an OCD thing.

gotten every achievement and dlc achievement for halo 3 , odst, and reach.