While some investors may be optimistic on Tesla’s Model 3 production plans, Goldman Sachs is concerned over slowing sales growth of the company’s current electric cars.

The report helped send Tesla’s stock down about 5 percent in the first hour of trading.

Goldman analyst David Tamberrino lowered his six-month price target for Tesla to $180 from $190, representing 49 percent downside from Monday’s close.

“We remain sell rated on shares of TSLA where we see potential for downside as the Model 3 launch curve undershoots the company’s production targets and as 2H17 margins likely disappoint,” Tamberrino wrote in a note to clients Wednesday. “This comes as demand for TSLA’s established products (Model S and Model X) appear to be plateauing slightly below a 100k annual run rate.”

The analyst cited how Tesla’s second quarter deliveries number of approximately 22,000 cars missed his forecast of 23,500 and the Wall Street consensus of 24,200. As a result, he lowered his annual growth estimate for the Model S and Model X cars to 5 percent through 2021 from his previous forecast of 13 percent per year.

Tesla blamed a production issue with its 100 kilowatt-hour battery packs for the second quarter deliveries shortfall.

“Further, cash burn should intensify as we progress through 2017 –though we forecast the next capital raise in 1H18,” he wrote.

Multiple Wall Street firms including Bernstein, KeyBanc Capital and Cowen also expressed disappointment over Tesla’s second quarter deliveries result in notes to clients Wednesday and Tuesday.

“Tesla’s Q2 production and deliveries report raised more questions than answers, particularly about Model S and X demand,” Bernstein’s Toni Sacconaghi wrote.

Tesla did not immediately respond to a request for comment on this story. Its shares are up 65 percent this year versus the S&P 500’s 8.5 percent return through Monday.

—CNBC’s Michael Bloom contributed to this story.