Ok I'll try to describe what happen to me: I was playing us sub mission 9, were you have to sink oilers and RNE and IMP are having a big fight. One Imp DD tried to drop DC above me but he was weak and wasn't going fast about 10 Knots. He got blasted by RNE while droping DC and he started to sink right above me! I ordered to ahead flank, hard to starboard and whent in spectator to see how thing were going with that DD sinking. I then ordered to dive to 100 meters, but i was suprised that nothing happened. I quit spectator and to my suprise I wasn't going anywhere, my syb speed 0 my engine still ahead flank and the arrow for dive was on 100m but I wasn't diving huh: . So i odered a dive dive dive, and all of a sudden the sinking DD was gone and I was going 45 knots backwards crazy: but must of all I surfaced but i odered to dive. Then all went back in order hmmm: . My sub went at periscope depth and I was going 9 knots ahead....realy realy strange. Anybody notice something like this. Because it's embarasing to surface with a sub when you've got 10 destroyer shooting all there guns around. Anyway I managed to finish the mission
or else its a bug of some sort, try see if you can reproduce it