Can't strengthen some skills (bug)

[tjomd]

So I've been strengthening my skills in the French tree, but got stuck at Possesives 2 and Demonstratives 3. Their strength is 4/5. I've already did them for, like, 7 times each, completely without mistakes, but they still won't strengthen. Both just keep 4/5, no matter how much times I try to do them.

Looks like a bug, because I can't really influence on it. Has anyone experienced this also? These two non-golden don't really look nice. :(

Thanks.

[BiaGranado]

a lot of people have that problem, Duolingo is hopefully fixing it