I know that mobile synchronization is very tricky and hard to implement, in general.
But current sync implementation of Memrise-apps (both iOS and Android) is one of the worst ones. There’re a lot of people complaining the same issue, over and over and over and over and over and over and over and over and over and over again, over the several years.
Why you smart guys do not listen?
It’s very hard to implement a proper seemless synchronization, yes, but it’s not impossible to give an appropriate user-experience for that matter.
A simple and easiest way is to put a “Reload” or “Sync” button, somewhere on the course.