For me unless the watchmen see the vessel I will not be able to lock onto it until they do I think this is the OP issue and there is not really a way to fix this all I can say is from playing stock RFB and TMO that TMO seems to have less occurrence of this than any other.I think it has more to do with the environmental mod and tweaks to crew "vision".
As to the whole "lock" thing well they sort of did have a lock because whomever was running the TDC could update the bearings the TDC gave(after inputting the target data that is) for the person manning the scope so the game is simulating this as best it can it is giving you an extra set of hands so to speak so you can do other things and not have to keep moving the scope to follow the target.
In a real sub the skipper had an entire crew of men to help him attack subs he was just the head of the chain and made the decisions if SH4 was a true simulator like what real US Navy submariners use it would take 20 subsim members to play the game maybe more.
And you can not pick up enemy folks in the water.
P.S.
Thanks for hijacking my thread.
I suspect you'd get more answers if you start your own thread.
What is the deal with that? an off shoot question/related topic happens all the time here on subsim better get over thread ownership real fast we arent too serious round here.