Homing torpedo went astray

[K-61]

Last night in my previous Kaleun's last patrol of the war I had an escort lined up for a perfect kill shot with an an acoustic torpedo. I can't recall which type it was, sorry. As the escort passed across my fore tubes, I fired the torpedo. To my horror and disgust, it made a 180 and sailed harmlessly away. My own engines were stopped, so it wasn't tracking on me. Any ideas? Do these things occasionally suffer from tracking errors? That destroyer captain had no idea how close he had come to being blown out of the water. Lucky sailor, I say.