I don't think they can stop your career before it even begins. One of my instructor had 7 fails, he is now flying for his national carrier. And I reckon he was a very good instructor. Another one failed meteorology three times, yet he got called to several interviews and now he is an A320 first officer (didn't have to pay for his TR). A friend of mine failed M&B, then retook it and got 100%, yet it's still a fail. He is now flying the 737.
I reckon that these exams, as much of a pain in the neck they can be, do not determine whether you will have a career as a pilot or not.