Tesla had issues with manufacturing, like everybody. That is why there are not more car companies. But they have mastered this and massively improved each generations, go look at the tear down of the 3 and the Y. They have managed to make China Model 3 cheaper and have achieved pretty good margin.

They continue to innovate and have been strategically investing in becoming a battery provider and building and expanding factories in all the important markets.

And building EV at good margin is defiantly not a solved problem.