I think the second ep of last season (where she's looking for the TARDIS), it got towards the end which I had seen coming for Some Time, and at precisely the right moment L's little mouth dropped open and he went "Oh! But...*blah blah whatever it was, something about the TARDIS phasing in at the right moment*", mere seconds before Thirteen explained that and it showed up. So, yes, terribly obvious for me but perfectly timed for a 7 yr old. Since then I have been way more forgiving about the clunkier moments :)