I am getting cut off
When I do timed practice, I always get cut off when I miss something, I will be about 12 problems in, I will miss one, and it finishes even if my timer is still running. Is this a bug?
If your timer still has more than about 10 seconds it's a bug.
10 seconds can get used up in getting information from the server.
So it comes down to your judgement - do you think you have enough time left for the program to contact the website, mark you wrong, and move to the next question? If you think whatever time you had left could get used up doing all that, it's not a bug. If you think it has enough time for all that, then it could well be a bug.