first off i was posting this on the wrong forum (SH3)
anyhow i encountered a few times sinking totaly damaged by unknown means and thus again read following:
ok, it happend again, on patrol at Iowa Jima, not moving, time compression up to 125 for about 5 minutes (RL) at periscope depth.
Nothing being detected, time compression to x1, i turn on silent running, 1/3 ahead, ping for bottom... over 1000 meter, change depth to 30 m (periscope depth was at 17meters) because i think i would get a better reading for finding ships at 30m depth, as soon i hitted 30meter depth, i take a huge load of damage in superb fast succession (crew start spamming damage reports like insane) and sink, game over camera before i can even act or hit the blow ballast hotkey.