I've been experiencing various problems on Lingvist on iPhone recently, which I reported to Lingvist (on Lingvist German from English, my "level" keeps going back and appearing as on level 1 even as I progress through the cards, but it doesn't affect what cards I get so it is just annoying rather than anything.)
I also get a congratulations pop up when I have done only 5 cards out of my 70+ repeat stack saying I have got 80% correct?
Anyway today I have a new bug. I have done almost 200 cards today but for some reason my progress is now showing as 0. I had done 5 cards before I noticed this and my progress has already reset to 0 again!
Luckily it doesn't look as though my number of words learned has gone down. Edit: just looked again and it's definitely dropped about 50 words off of my number of words learned. :(
I hope that the bugs get fixed because there are quite a lot now.
I tried uninstalling and reinstalling but it didn't make any difference. I only get this with German from English. I have been using French from English for ages, I have nearly finished and have never had a problem with it.