update with the save bug I had.
It seem that whenever I tried to approach the convoy in a certain area the game would ctd no matter what.
I tried went further on its predicted path and intercepted 100 km further away, and no bug, I could make my attack. ( had 3 torps left, first was a dud and other two missed because they had time to hit the break as I didnt time them properly)
I kept making saves along the way, reached my port without a crash
I think if the weather is demanding ( fog and rain probably) + large convoy there is a very high chance of ctd.