Recently I've been encountering a problem in which the answers at the bottom of the page will fall out of sync with the questions in the centre. There is actually an overlap of the graphics. The Skip button is partially covered by the answer and checkmark from the previous question (the red or green background colour doesn't show). At the same time the sound quits and the speaker graphic no longer appears. I can't get past the Type What You Hear questions without typing some random guess in the box. Sets me a long way back if I hit three of these questions in a row. I'm using Firefox on Ubuntu. It has only been happening recently, perhaps since you changed the progress graphic at the top. Otherwise, it seems to occur randomly. I've been opening DuoLingo full screen because that allows me to see the answers without scrolling each question. It crapped out on me today over both lessons I attempted so I'm frustrated and done for today. Tomorrow I will try without opening full-screen and see if that has an impact.