I seem to remember having this issue on Windows (using either Firefox or Chrome, I can’t quite recall), but I’m currently experiencing it on Firefox in Ubuntu 16.04. What happens is I’ll submit my response, it’ll pass the checks, then tell me I can proceed to the next exercise. When I click (or Ctrl+Enter), I get the little moving circles loading animation, but the page won’t load until I refresh and submit again. This seems to happen every two to three exercises. Anybody else experience this? Is there a workaround? Thanks!
If there isn’t one already, please create a detailed GitHub Issue for this problem.
I’ve had the same thing, but I’m in China with poor connectivity & assumed that was the problem.