Oh, i forgot to say that the magizoology bug appeared in 5.4.0 Mod apk, when i reached Lvl 8From what I've seen the bug is common enough that some legitimate players will have reported it to JC, so hopefully it will get fixed.
If it doesn't get fixed, the only other solution that I know would be to get to hogwarts beyond, as in volume 6 you unlock a repeatable method of gaining magizoology levels. I think that the beyond update might actually be what broke the levels in the first place, as they changed how the magizoology level works. In volume 6, it becomes a skill tree along side auror and healer and the max level for it becomes 20, where you need something like 300000 xp to reach it.