I am getting this every now and then. Unfortunately I have been unable to solve it or determine the cause. I have posted a few times but noone seems to know how to fix it.
I can only say save often, save surfaced right b4 you submerge and than save submerged b4 an attack and during one as well. I am usually running 5 or 6 saves a patrol just to avoid restarting a whole patrol because of CTD.
Once and awhile I CTD when I load a saved game. I then go to an earlier save and CTD again. I may have to go back awhile in the patrol b4 I get a good save that works. Almost like the issue is time travelling backwards through my saves and corrupting them somehow.
But I am in agreeance with you, the majority of my CTDs were after I engaged a target. Then when I reload the saved game its only a few seconds b4 I crash or it never even fully loads.
If you find out what it is or how to fix it plz post! GL!