I recently completed this achievement and was frustrated by the bugs (miss, out of sight, hitting other targets). The trick I found was to choose a target each attack phase and fire continuously; do NOT change target unless your target gets destroyed. All of the videos are outdated, change targets, and never miss. The first phase I targeted the center of the back, the second phase I targeted the nearest point on the left wing. All shots on the first half of each attack phase will miss, just keep firing.
I parked a character at this location and logged in periodically. Eventually I got a map that wasn't bugged and finished the achievement. Took around 5 days.