When an AK-74 is equipped with a GP-25 grenade launcher, performing the Unequip action causes the GP-25's sights to become misaligned. This can also be triggered by entering a vehicle or switching to another weapon.

The issue can be resolved by re-equipping the GP-25.

When inspecting the weapon model using the in-game Armavision, it is clearly visible that the dial on the sight has changed. I have attached four screenshots named "Normal" and "Problem" for comparison.