I've run into this issue before when using GFO, as well as one where an approaching high speed convoy of four large transports begins blinking on screen and losing one or two members before I can reach attack position; both then led to crashes. Never found a solution to either. Afterward I went back to stock and had almost forgotten this.
Once I encountered this at short range, popped up to periscope depth and saw dozens of DDs streaming by. Went to camera view and headed up the direction they were coming from; I stopped when I realized there were easily thousands of destroyers. Took a deep breath, picked out six targets, and let loose an entire salvo, expecting a memorable response. Instead the entire system crashed before the first torp struck.
