We’re currently experiencing crashes across all versions of the Memrise iOS app due to a problem with the Facebook SDK. This is a widespread issue across all apps that use this FB SDK for features like Login via FB.
Our developers are looking into the problem, though it’s worth noting that this is an issue introduced by the 3rd party. We are nonetheless working on a fix to be released asap.
We’ll keep you updated on this thread. Thanks for your patience.