Can't mark lesson as complete

[andreyromanchev3447]

Hello guys.
I check "Mark Lesson Complete", got the tick in field.
But when I open this lesson again, the mark is missing, lesson is not complete.

This started last week, when I purchased premium subscription.

[andreyromanchev3447]

Yup, marking is completely broken for me.
I just mark off some of previously completed lessons and can't mark them again.