No big secret there, early war MK14s are pos. They do improve quite a bit as the war progresses though, but there won't be anything radically more reliable available.
You can however greatly, really almost a night and day difference, improve their reliability by remembering a few things when firing. These are especially important early in the war:
- Always use the slow speed setting
- Make sure the torpedo track angle is as shallow as possible(early war). No kidding here, early war MK14s have a 100% failure rate at TTA of 90 in RFB.
- Use the shallowest depth setting possible