Tesla’s stock price plunged 14% on Thursday after the car company reported negative free cash flow of $1.1 billion despite revenue rising 26% from a year earlier.

CEO Elon Musk sounded rather odd on the earnings call Wednesday evening, especially when it came to Optimus, his humanoid robot. Gone was the bluster and cockiness of a man who’s claimed there will be 10 billion robots by 2040. Everything that came out of his mouth sounded like a warning that Optimus might take considerably more time than he first promised.

“Optimus, as you’ve heard me say before, I think Optimus will be the biggest product ever. But it is a very complex problem to solve,” Musk said on the call.

The Tesla CEO went on and on about how…