You have to read the dungeon description carefully. Some only go from lvl1-49, then you got already 51-59 and just "only lvl 50" is another category. Same with lvl 60 and 70. It is random which stickers you get, they are not always the same. Could be that you got the 61-69 sticker. And if you are a returner you most likely don't have all 70 unlocked yet, so you don't have that roulette yet?

Ofc it is still possible that you have a bug, but I would really check your stickers first, it is not clear immediately.