Escorts can be sneaky.
It is their job to protect ships and blast you out of the water.
Just because escorts are surface ships and not subs does not mean they cannot try to 'go silent' and listen for their prey.
Heck, be wary of suddenly hearing a lone merchant shortly after escorts have apparently left... keen ears can reveal treachery afloat on the surface.
Patience is a virtue, especially when hunting in a sub.
Haste and greed can be deadly when in a sub.
I sometimes prefer to avoid such attacks. The skipper needs to remember that making sure his crew gets home alive is as important as sinking enemy ships.
Need sub to sink lots of ships, not a single sunk ship and a dead hero and the US down a sub.
In such situations, if attacking again just increases the risk of being found again, I will choose to mark the crippled ship(s) on map with a several hundred yard diameter circle around them, and go deep and try to sneak away.
After some fresh air, a little recharging and all tubes reloaded, I will sneak back to finish the job, fresh for a fight, hoping the target is still there.
If not, oh well. If so, time for more fireworks.
He who runs away lives to hunt another day.
I have messed up with torpedoes myself, it is annoying, often initiating a facepalm maneuver, but it happens.
I have been very tempted to go back to SH3 myself... never had corrupt save troubles with it... IMO it actually has a better interface and feel than SH4 (better/more defined controls and options, such as checking for weather, navigation options, having a separate 'fire at will' and 'hold fire' for Deck/AA guns, options and the 'fire at long range' setting...)
*evil eyes SH4 case*