Impossible. I just cannot evade destroyers…

I’m playing SH5 with TWoS, manual targeting, everything is set to the “hard way” except from map contacts, which I do have set to “on”. The problem I have is the following:

I find a reaaaally nice convoy, plenty of big ships. Once I’ve launched my last torpedo I start to dive and go silent running while turning away from my “firing position”. I hit 3 of my 4 torpedoes and three destroyers start looking for me (it was night time and one of my torpedoes was a steam one) so they go to the place where the torpedo came from.

Meanwhile I’m 90m deep at 1kn completely silent. They arrive to the area, everything’s fine, I made no noise, they shoudn’t know if it was fired from 1000m or 5000m. For some reason they guess where I am and start pinging me. From what I’ve learned, once they’ve pinged you, they know exactly where you are, so you better get out of there.
I go maximum speed and hard port (or starboard) to change my heading until they stop pinging, then I go to silent running again.
They start to drop some depthcharges on me which I dodge by turning and speeding, then I go to silent running again.
I keep doing this for like one real hour until they start to get REALLY accurate, they don’t let me go anywhere, they’re constantly pinging, they keep dropping depthcharges just where I am, I cannot really do anything, I try to dodge them but they ALWAYS hit me eventually, doesn’t matter if I accelerate, I turn, or I do a barrel roll.

AI Bot running SUBSIM, what could go wrong?!