Had the same issue a couple of times. Once for me and once for a friend of mine. When you get to a certain point even after passing several exams together, the error occurs.

The first time it happened, I saw that my friend had already passed the exams beyond where the bug took place. He passed them with other people. The same with me (at another time) when the bug occurred; I had already passed those levels with others when the bug occurred.

It could also be a cross-server bug as those from the same server were able to bypass the bug when it popped up (I'm in a merged server). Whether I'm wrong or right, it's still a bug and it keeps us from helping other people in team exams. Please fix.

Thank you sincerely, I learned something. Next time I'll check the assists and will pass this info on. I now concede this is not a bug and thanks again for sharing your insight.