I found a bug I believe to be introduced since the latest update, because before I could not produce that one. It goes like this (had that today): You start a quest like experience on level 1 just before it changes to coins. So you finish it and once you are back you are in the coins quest and seem to have completed level 1 there, although you started the XP one. Then about 4 hours later I started the coins quests, starting the last one (level 5) about 2 minutes before it ended. I was glad I made it because I needed the coins. But when I finished it it said I won a lot of fish. And it showed I finished the level 5 fish quest and with 3h58m remaining and I could not start any of the fish quests any more. Unfortunately I also needed the fish a lot and was quite frustrated.
Before the update I could start quests just before it changed to the new one and nothing like that happened.