Offline practice progress always deleted when back online
The offline practice mode of the iOS app has been much improved in the latest round of updates- it had become completely unusable, and is now reliably downloading the necessary lessons, etc. However, it always deletes one lesson when the app is opened up again with internet access. For example, I completed the section Objects from the German course (two lessons) while my ipod was offline. I was rewarded three lingots and the lesson turned gold. When I got back online, the lesson turned from gold to blue, saying I've completed 1/2 lessons. This has happened to me three or four times now, and it's always one lesson that's deleted. So if I do six lessons offline, the checkmark on the sixth lesson will disappear when I go back online (I've watched it go away, such a bummer), and the other five lessons remain as completed. If I do one lesson offline, it will be deleted as soon as I'm online again. It doesn't seem to matter if I go online again on my device, or try to refresh my progress on the computer version, I always lose one lesson.
I'm using the latest version of the app on iOS 7.1.2 on an iPod touch.
It's 2019 and this is still happening. I had finally finished a really frustrating and long-feeling skill, and finished am easier skill also while offline. I'm back online now, and lost somewhere around a dozen exercises. I even took photos of getting the gold on them, I was so excited. Now I have to redo it. Duolingo plus - not worth it if the offline functionality is a black hole of effort. Especially when the progress quizzes are not at all relevant to what content I've actually covered.