Tesla CEO Elon Musk disclosed another $3.6 billion in stock sales on Wednesday, taking his total near $40 billion this year and frustrating investors as the company's shares wallow at two-year lows.

A U.S. securities filing showed Musk unloaded 22 million shares of Tesla over three days from Monday to Wednesday. The sale is the second big chunk of stock he has cashed out since his $44 billion purchase of Twitter in October.

Tesla's stock fell to $157.67 on Thursday, down more than 55 percent for the year, underperforming both automakers and the broader tech-heavy Nasdaq, which is down about 30 percent this year.

Both RBC Capital Markets and Goldman Sachs lowered their price objectives for Tesla, citing softer demand and the stock's continued pressure from concerned investors.

"Investors are concerned about demand, pricing, auto-GMs (gross margins) and Twitter distraction/overhang/impact on Tesla brand," said RBC Capital Markets, slashing its price target by $100 to $225.

Meanwhile, Morgan Stanley lowered its estimates on electric vehicle (EV) market penetration as EV makers' shares continue to fall.

Morgan Stanley analyst Adam Jonas expects EVs to account for 11 percent of the U.S. auto market in 2025 and 26 percent in 2030, according to a new note released Wednesday. That's down from his prior U.S. EV penetration forecasts of 13 percent and 32 percent, respectively.

A weak global economy and high battery costs are raising concerns about EV demand in China and Europe as well, Jonas noted.

Tesla is offering discounts in the United States and China, two of its biggest markets, to boost demand.

Musk said Tuesday that, "Tesla will be great long-term, but doesn't control macroeconomic tides."

Musk's fortune, mostly tied up in Tesla shares, has fallen with prices this year and he briefly lost his title as the world's richest person last week –according to Forbes– when he was overtaken by Louis Vuitton boss Bernard Arnault.

(With input from Reuters)