What if the Captain has issued strict orders that no change in course is to take place without his approval. In other words, “Wake me up and you’d better have a damn good reason for doing so.”
“Those towing lines were defective!”
Then he's an idiot. But even generally, "no change in course" won't be considered to apply to dodging obstacles, and then resuming initial course/speed. That is a common occurrence because fishing boats, etc., pop up all the time.
I cannot imagine -- outside of a movie or actual insanity a captain issuing specific orders barring the OOD from taking action to avoid a collision while he's asleep. And if he did, the OOD's proper response is to avoid the collision anyway, accept the consequences, and then request Admiral's Mast if necessary.