When entering and exiting "Aim Down Sights" the camera will abruptly Zoom In and Out for both actions. The reason for this is because the input for Zoom/Focus is shared with ADS.
Zoom/Focus is dependent upon a trigger threshold and zooms based on how much it is depressed. This is fine, but there should be a small window where zoom/focus does not fire if the input is pressed quickly to a "full pull" so this action does not occur when entering/exiting ADS.
This heavily impacts combat and overall game experience for players. It has functioned this way since launch, I've also spoken with players on Xbox and it is the same on that platform.