Dark Dungeon doesn't lvl up after defeating last boss.

I've cleared dark dungeon lvl 1 20 times or so (one or two stars, never 3). But it doesn't lvlup to 2 lvl. There is in game tip "increase or decrease dungeon lvl depending on clear or defeat". Looks like it doesnt work. Any ideas about this bug?

Try to win with 3 stars.

Finally i won with 3 stars but i'm still on lvl 1 of the dungeon. Any other ideas?

You have to increase your attribute levels and stage level as well. Then the dark dungeon level will rise too