I was just playing a short mission. I was chasing Able while my buddy went after Baker. Got a volley of depth charges fairly close, but not a kill. Continued to chase Able. He surfaced and I started letting him have it with the guns. Two direct hits with accompanying explosions. And suddenly ...
Catastrophic Defeat
Convoy Losses: None | No Ships Lost
U-Boat Losses: Critical | 8 U-Boats Sunk
I probably had 2/3 of the mission time left.
***EDIT: When I clicked on the above screen, the animation showing a U-Boat torpedoing a convoy ship played again. Then it went to the "Thank You" screen and the game froze.
Otherwise, I'm loving the game so far!