This is a bug that I reported on in the tests for both Halo 2 and 3 and still has not been addressed. I just bought a brand new xbox one controller today to make sure it wasn’t my hardware, and it still happens. Playing the game on the platform it was made for doesn’t even work properly? Seriously? This happens on both the left and right sticks. The drift is so bad that using any precision weapon is impractical.
What are your dead-zones set to?
If you go to the controller calibration app on Xbox, do you see your sticks drift?
I play in all games with 7% of dead zones, because of that.