Yep. Sorry about this. Previously reported. (Although you were one of the previous reporters )
An upgrade I think changed how hints/answers were rendered when they contain angular expressions. They're basically not.
I can and have fixed one challenge by escaping them, but that's not an ideal solution, so I've asked a senior developer to check this out and figure out a better solution.
Please ask if something is still confusing you, and for now post at this forum if you have a question. You can use the contents page in the course to move to other challenges if you get stuck.