I have version 1.4 of the game, uniform-, emblems- and VIIB texture mods installed (...nothing that should affect gameplay, you know...).
Today I sank a C-2 in Dover, it was the only ship there. Then I looked around, two destroyers coming in from the south, everything fine so far...
But then came bug after bug...
1. Two more burning, half-sunk cargo ships appear out of nothing in the harbour, one burnig, half-sunk destroyer appears from devil-only-knows-where on the bottom of the harbour entrance. (?)
2.
While checking my crew-screen, I notice I have four man on the bridge - in periscope depth. (?) 
Checking the free camera confirms this, four men, several meters below the waves enjoying the view from the conning tower...
3. The two destroyers coming from the south almost smash into the pier, one heads backwards, then again forward almost crashing into the pier, back, forth, back....and so on...
...the other drives slowly backwards for a mile or so, when one of my torps hits her ass...
4. The other stoopid destroyer plays his forward-backward game until one of my fish shows mercy by sinking her...
5. Surfaced now I head westwards, noticing impressive coastal batteries - but they don't fire. There, right in front of them I am, 1 mile away, surfaced, an easy prey...they just sit there and do nothing...
So...why is this...does nobody ever test stuff like this ?