Tesla Motors CEO Elon Musk says a smooth, regular production flow of just over 400 luxury electric Model S sedans per week "feels so much better" than the crunch time the company endured in Q4, with nearly 70-hour workweeks and sometimes a "tragedy of errors" getting in parts from suppliers abroad. Tesla (TSLA) late Wednesday reported a bigger-than-expected Q4 loss, and the stock was down 10% in afternoon trading Thursday. But Tesla hit production