"When it comes to auto production, Elon may have fallen in love with the wrong thing. He's fallen in love with robots and automation," Max Warburton, European autos analyst at Bernstein, said in a Wednesday report.
"There is a body of academic and practitioner research on" how automation is often contrary to the principles of lean production, Warburton said. "It appears [as] though Tesla has chosen to ignore it. Or perhaps Tesla is convinced it's out of date, in an age of better sensors and computers."
Tesla shares fell nearly 7.7 percent Wednesday, off more than 30 percent from its record high hit in September. The stock has tumbled 14.5 percent this week following an investigation into a fatal Tesla crash and Moody's downgrade of the electric car maker's credit rating.