I have this issue on my '11 with 90k on it and it has done it occasionally since new. What I think it is, is that the transmission is programmed to try and hold a higher gear as long as possible for optimal MPG and doesn't shift from 2nd to 1st quick enough and makes a hard shift at really low speed or at a stop. I only notice it on the 2nd to 1st down shift.
I'd bet if you could get a performance tuning that altered the eco biased shifting it would go a way. If you watch it shifts in the next gears at a really low RPM, way lower than you would if it were a manual. I think they're just trying to squeeze every MPG out of it, even as bad as it is.