Energy is used like you are moving when aiming down the sights of your gun as a stalker cloaker. This shouldn't be considered moving
I play Infiltrator with Stalker cloak a lot and have experienced this as well. While I do not know if it is a bug or not I can tell you what the cause is. You are on "uneven" terrain. Move a smidge left or right, up or down and test your position before hanging out. If you are in a precarious position your cloak will count down while aiming. Hope this helps.
