I do not know if it is intentional or not but I will go with my gut feeling that it is intentional and hardcoded somehow, which is at the last sticker for every different album (8/9), for some reason the probability of getting the last sticker is much, and I mean MUCH smaller than the other ones, because in my experience, the first 8 stickers were very easy to obtain, each pack I opened I got a new sticker (including even if I got like 6-7/9), but for some reason if the sticker collection hits 8/9, I seem to not get the last one (As you can see in img the upper row, only 2 of them are filled, even though I have been opening a ton of packs). After opening daily packs (almost all of them), I am almost certain that the last sticker for each collection is very hard to get, even though is possible. This is probably to make players spend more time on the game but I think it is kind of frustrating and far away from the sweet spot. I suggest change the probability of getting the last sticker in each collection a bit higher, so that it is still hard, but not near impossible. Thank you.