In a busy news day for Tesla CEO Elon Musk, the National Highway Traffic Safety Administration (NHTSA) announced it is investigating Tesla vehicles over “phantom braking,” which is when cars unexpectedly brake while in Tesla’s Autopilot driver assistance system. The investigation covers roughly 416,000 Tesla Model 3 and Model Y vehicles model years 2021 and 2022. According to NHTSA, the agency’s “Office of Defects Investigation (ODI) has received 354 complaints alleging unexpected brake activation.”

“The complaints allege that while utilizing the [advanced driver assistance system] features including adaptive cruise control, the vehicle unexpectedly applies its brakes while driving at highway speeds,” NHTSA wrote. Complainants report that the rapid deceleration can occur without warning, at random, and often repeatedly in a single drive cycle.”

This is not the first time Musk and Tesla have been under NHTSA investigation. Back in August, NHTSA opened a separate Autopilot investigation into 765,000 vehicles after a series of crashes involving Tesla vehicles and emergency vehicles. In January, NHTSA announced an investigation into Tesla’s “Passenger Play” feature. The feature, found in various 2017-2022 Tesla Model 3, S, X, and Y vehicles, reportedly allowed drivers to play video games on a screen while the car is in motion.

As the latest NHTSA investigation begins, a lawyer for Musk and Tesla is turning his attention to the U.S. Securities and Exchange Commission (SEC). In a letter to a district judge, attorney Alex Spiro accused the SEC of “endless” harassment, saying the commission is “issuing subpoenas unilaterally” without court approval.

“Worst of all, the SEC seems to be targeting Mr. Musk and Tesla for unrelenting investigation largely because Mr. Musk remains an outspoken critic of the government; the SEC’s outsized efforts seem calculated to chill his exercise of First Amendment rights,” Spiro wrote in the letter.

The judge Spiro wrote to oversaw the settlement between Musk, Tesla and the SEC over a tweet Musk sent back in 2018. The tweet hinted at potential buyout of Tesla, when in reality a buyout wasn’t close to happening.

“Am considering taking Tesla private at $420. Funding secured,” Musk tweeted.

He and Tesla had to pay a combined $40 million in civil fines. Earlier this month, Tesla revealed it had been subpoenaed by the SEC about the company’s compliance with the settlement. The SEC also subpoenaed Musk over a Twitter poll he posted last November.

“Much is made lately of unrealized gains being a means of tax avoidance, so I propose selling 10% of my Tesla stock. Do you support this,” Musk asked his Twitter followers. The poll triggered a massive sell-off.