This started happening to me as well. Usually when a new multiplayer game starts (after having played multiple matches) the aim starts wandering left or right or up or down. My PC mouse is fine because exiting the game I can use the mouse normally to select menu buttons. Something in the game is causing it.
This is a different problem which I had in the beta. The fix was to remove the Microsoft game pad device under devices - this stopped the drift. For more info there are some YouTube’s and posts on the internet that cover it.
