Whenever a vehicles turret is starting to turn, there is a small crack to be heard. It's even more producable when there are more sounds playing in the background. When the turret is still and not moving, no cracklink noises. As soon as the turret starts turning, there is a small crack or multiple cracks.
This is reproducable with any turret related vehicle, from HMG Hunter to MBT1. The sound file itself is ok, and even replaced by a new sound file or an empty "muted" track the crack appears to happen anyways. Which leads to be a general trigger/controller problem, unrelated to the soundfile itself.