as the summary says, when a player aims through the RCO's magnifying scope (not collimator sight), if the weapon is deployed (edit: while prone), and the weapon is aimed at a certain angle, the player's view is blocked by one of the straps of the Carryall backpack, if it is equipped.
a video of this issue reproduced: https://www.youtube.com/watch?v=8AnBygc7p8Y