If the bug is with the app
Make sure that you are using the latest version of the app via the App Store (for iOS) or Google Play Store (for Android).
Then, try logging out and logging back into the app to force it to sync with the server - note that this removes any downloaded courses in the app, but you can re-download them.
If the bug is with the website
Make sure that you have the latest version of your internet browser and Flash player. Also, try clearing your browser's cache and cookies.
If that does not help, try using a different browser (e.g., Google Chrome) and let us know if you had the same problem, or not.
How to report
If you are still experience issues, please submit a bug report by filling in the form found here: https://goo.gl/forms/ARUn1XuSBgXL80dj2
This sends the report directly to our developers and QA team, who can then work on getting it fixed. Once the report has been submitted, feel free to browse our community forum where you may be able to find solutions to the bugs raised: https://community.memrise.com/
Due to the number of bug reports we receive, we may not be able to reply to every one so please bear with us.
Your patience and support is much appreciated!