1. Equip weapon with scope that has a backup sight.
2. Aim down the optic, note the chromatic aberration that appears to the sides
3. Swap from your optic with "/", note how your backup sight is still effected by CA where it doesn't make any sense - obviously you don't get CA with your eyes.
4. Come out of aim-down-sights, and then go back into it now that you have backup sights selected.
5. Note you don't have CA, as is normal for the backup sights.
6. Swap to your optic with "/", note how now your scope does not exhibit any CA.
7. Determine that the game is not looking up which PPEffects to display when swapping optic whilst aiming down sight.