ODST "Classic" acheivement is broken

The Halo 3: ODST acheivement “Classic” says to “Finish any level solo on Legendary, with no shots fired or grenades thrown.”. I hopped into the “Street Smarts” playlist which is the Mombasa Streets segments on legendary and did the first 2 missions, with the only combat used being melee to clear the required areas, no grenades used, no shots fired, and I still have no achievement to show for it…

Uplift Reserve is the easiest place to get this achievement. Get on the hog and gun it. Just to be safe, dont even let a marine in the back. Go all the way until you find an abandoned ghost (this will make things alot easier). Then get through the level on boost non-stop.

I believe the problem is you aren’t in an actual “level”, just a checkpoint within a level itself, as Mombasa Streets has 9 checkpoints within it if I remember correctly. You need a story level, effectively.