The price action today is fascinating. This is my interpretation of what has happened so far.
Firstly, if you look at the shape of the TSLA and NASDAQ charts, they are very similar, but show clear evidence of what
@Papafox calls "Dip on Steroids". That is, when the price is dropping, someone piles on to make the dip go down as fast and as far as possible, which is stupid behavior if you want to get the most out of selling lots of shares. But it isn't stupid if you're shorting the stock. It looks to me like they tried to halt this behavior before triggering the uptick rule.
Then something happened that was either really stupid, just coincidence, or really smart, depending on who did it. A minute of heavy selling triggered the uptick rule, and the stock immediately started climbing again. Coincidence is possible, it corresponds exactly to the same drop in the NASDAQ. If it was a short, it was stupid to trigger the uptick rule. If you are really sure that the S&P500 announcement is coming tonight, and you're long, it would make a lot of sense to dump some shares, trigger the rule, buy back, and watch the fireworks overnight.
TL;DR -- I have no idea. But the trading chart looks very different after 13:43EDT than before it.