Beware going to someone's profile while mid lesson.
This has happened to me a few times and I keep forgetting about it. If you are mid lesson and enter the discussion page and then click on someone's avatar you will be totally bumped out of the lesson. I was two questions from finishing and lost everything. It would be nice if this glitch was fixed. Very frustrating.
Right-click on the profile link, then choose "Open link in new tab". That way, you can visit the profile without losing your place in the lesson.
I believe that is mat not actually be a glitch. It might be meant to keep you from cheating. I'm not entirely sure, but I think that's what happening. I hope you don't suffer from the same mistake again.