Well, I was making Cleansing with poisons and decompozers, when i noticed that one of the pink snakes reappeared after Zone refresh.
I clicked on it again and you know what? It rolled back the pink snake removing but did not return the stinky poison!??? Thanks to this bug I got the quest failed because it used stinky poison twice on the same snake!!! This quest was a part of weekly challenge so I'll wait to see one of them assigned done!!!