I have exactly the same problem. Actually it has been the case for more than 1 month (since I installed the application on my phone). I thought this bug would probably already have been reported.
2.9_3820_memrise
Moto G - Android version 4.4.4
Play Store
Yes, it can happen on any course leaderboard. I don’t know if it’s on all course leaderboards since there seem to be a few conditions (like “having enough people ranking better than me on this leaderboard”).
In my case it can happen as soon as they are too many people with a better ranking on the leaderboard. I never had this problem when scrolling down, but scrolling up gives this result. On the other hand, I don’t usually scroll down so maybe I just never realized…
It doesn’t always happen in the exact same way (I guess sometimes the application manages to load the names of people better ranked than me), and sometimes it doesn’t seem to happen. I just tried twice : in one case, I managed to load all the leaderboard, in the other case, it started looping again when I tried loading the names below 20. Maybe it has something to do with the speed at which I scroll up since in the first case I was going slowly to check when exactly the bug would appear?
I reported it some time ago, and I have been told that they are aware of the situation.
It is a weird leatherboard. The options for periods is integrated to the scrolling and that causes the problem. It happens all the time in my app an the ranking is half-illogical.