musical expression quest

I have been having a problem with some of my quests. For example I am doing the musical expression one right now. My baby has been playing the xylophone for DAYS straight. I literally have him do nothing else, I have even used LP to finish my task early so he can start again before I go to bed. I am six hours away from finishing the quest in the time they give us but I am still missing 3 of those things u earn and need to collect. What I don't get is how several times my SIM has completed the task and did receive anything. I see the go by levels but my sims music level was the level I needed or higher and I still didn't get anything. It's frustrating to do a quest pretty much non stop for DAYS and not be able to finish it and get the rewards.