Duds in GWX

[EM2(SS)]

Just started a new campaign. VII in St Nazaire 9/40. Gonna try selecting duds on for a total of 84% realism.

So my questions are does GWX model itself historically, in that eventually the bugs are worked out of torpedoes and they are more or less very reliable?

If that is the case what date is that?

And finally are magnetics less reliable than contact during the " dud " period?

Thanks in advance