Could the demand for the Model S be fading? Since its first full production year in 2013, Model S sales have climbed pretty much each each quarter of each year. That seems to have changed and now, for the first time, the first two quarters of 2016 have shown a decline in sales. This decline drops well below Tesla's biggest numbers (17,272), which were in the fourth quarter of 2015. Models S sales for the 2nd quarter of 2016 reached only 9,745 and Tesla hasn't seen that low since back in 2014. Even if you add in Model X sales that could be taking some of the limelight and production from the Model S, the totals are still quite a bit below their peak.
This graph from electrek shows Tesla's Model S and X quarterly deliveries: