FYI, here is a pic using auto TDC:
As you can see, the TDC (white x with AOB line) has a perfect track on the center of the ship, yet the torpedo hits the stern. This can be repeated over and over with no variation in the torpedo's behavior.
Furthermore, behavior in manual TDC is identical (if you can work the TDC long enough to get close to such a perfect track). Torpedo will fall behind in the exact same manner as with auto TDC. TDC speed, AOB and range track are fine in auto and manual (although stadimeter range measuring in manual seems wonky and must be compensated for using map updates). The torpedo follows the gyro angle computed at the moment of firing properly. The calculated gyro angle is
wrong (at least with targets moving L to R). Here is a pic of the same situation with manual TDC (note that due to the resoluation of the stadimeter control, exact range will not be obtained and track will be either slightly to the fore or to the back of the target, however at this range it has no significant impact on torpedo track (will hit within meters of the same point regardless if range is a bit short or long):
As you can see, all four torps are on track to hit at nearly the same spot on the stern. All four had tubes opened before each shot. All four had a bearing/range update just before launch.
As has already been noted, this only seems to affect Mk. 14s at the high speed setting. Low speed will strike center of target repeatedly under the exact same conditions. This suggests that the sim is not calculating the correct gyro angle for the high speed setting of the torpedo for some reason. Perhaps it is using a different (higher) speed than the torpedo is actually travelling at?