Students having to repeat work.
Some students are complaining that their work on lessons is not being saved, and when they log out and then back in the next day they are taken back to where they began the day before.
Anyone else having this issue?
They could be talking about their skills weakening. This is a key part of how Duolingo works; a skill that isn't gold any more needs to be revised by clicking on the skill and then choosing strengthen. The aim is to keep the course gold.
Duolingo uses a spaced repetition approach. It shows you things you've learned at times that will most help them stick in your head. If you keep the tree gold, you'll find it works really well. Sometimes that means you don't make any progress through the tree for a while - that's fine.
Duolingo takes account of how long it takes you to answer the question, and it takes account of whether or not you "peek" - whether or not you hold the mouse over a word to see what it means. When you can answer the questions quickly and without peeking, the skills will decay more slowly.
After your students have strengthened the skills a few times, they'll start decaying more slowly, and then they'll be able to get further through the tree.