There aren't many stocks on the market that polarize investors like Tesla, Inc. (NASDAQ: TSLA). Elon Musk's electric vehicle and energy storage company has captured the imagination of millions of EV buffs around the world. Along the way, Tesla has burned through billions in cash on the back of investors eager to fund the company's ambitious growth plans.

For all of Tesla's growth and the disruption it's causing in transportation in energy, investors will eventually need to see Tesla make good on its manufacturing promises. And it's that execution that gives me pause in buying into Elon Musk's very expensive growth plans.

Image source: Tesla.

Warning signs for any company but Tesla

If Tesla is going to be a winner for investors long term, it's going to have to make money making cars and batteries for energy storage. After all, this is a manufacturing company, and it will have to make a return on the investment it's making in building manufacturing facilities. That execution is where I get nervous about Tesla; here are just a few of the reasons:

• Constantly missing deadlines: Tesla has never launched a product on time. In the last few years alone, we've seen the Model X come out late, the solar roof sit in production limbo, and now the Model 3's mass production be pushed back by six months, depending on how you measure delays. All of these delays wouldn't be a problem if it weren't for the fact that Tesla spends billions to build factories and is delaying any revenue from that spending -- and that delay allows competitors to catch up. By the time the Model 3 reaches full production, a dozen fully electric vehicles may be on the road.

• A revolving door of executives: If Tesla were the great company investors seem to think it is, then executives should be dying to work there. Lately, it seems like they're dying to get out. CFO Jason Wheeler left in early 2017 after less than two years on the job. President of Global Sales and Service Jon McNeill left in February 2018. Chief Accounting Officer Eric Branderiz also left this year, leaving over half of his $5 million hiring equity grant unvested. Maybe more startling, Musk's cousins Lyndon and Peter Rive left Tesla only months after SolarCity's buyout was complete, leaving the solar arm a shell of its former self. This list just scratches the surface of executive departures and is unnerving for any large company, much less a company with Tesla's growth goals and disruptive potential.

• Quality isn't up to global standards: Tesla has long had quality issues at launch, dating back to Model S handles that would lock customers out of cars to Model X vehicles that had faulty falcon wing doors. Now, early Model 3 deliveries are showing similar quality issues. Launching a vehicle whose doors don't line up correctly, or that locks people out of their cars isn't normal in the auto industry, and as more competitors launch EVs, and Tesla moves down market, these faults may not be as charming as they used to be. Consumer Reports already says the Model S is "not recommended" on reliability, and that's a big flaw in Tesla's long-term growth thesis.

• SolarCity acquisition has been a boondoggle: It's hard to say the acquisition of SolarCity was anything other than a boondoggle. A year and a half after the buyout, SolarCity is a shell of its former self and has lost its No. 1 ranking in U.S. residential solar. On top of that, the solar roof that captivated the imagination of those in energy is apparently in production, but there's precious little public information on the product and no apparent scale for the product. If you ask me, Tesla is slowly shutting down its solar business and letting competitors take its share.