DETROIT (AP) — An Apple engineer who died when his Tesla Model X hit a concrete barrier on a Silicon Valley freeway had complained before his death that the SUV’s Autopilot system would malfunction in the area where the crash happened.

The complaints were detailed in a trove of documents released Tuesday by the U.S. National Transportation Safety Board, which is investigating the March, 2018 crash that killed engineer Walter Huang.

The documents say Huang told his wife that Autopilot had previously veered his SUV toward the same barrier involved in the crash on U.S. 101 near Mountain View, California.

Autopilot is a partially automated system designed to keep a vehicle in its lane and keep a safe distance from vehicles in front of it. It also can change lanes with driver approval. Tesla says it’s a driver assistance system and that drivers must be ready to intervene at all times.

Huang's widow, Sevonne Huang, and his family are suing Tesla and California’s Department of Transportation for allegedly failing to maintain the highway.

“Walter said the car would veer toward the barrier in the mornings when he went to work,” the Huang family's attorney wrote in a response to NTSB questions.

The attorney also wrote that Walter Huang described to his brother Autopilot's malfunctioning “in the same general area where the crash occurred" in addition to talking about Autopilot problems with a friend who owns a Model X. Huang, a software engineer, discussed with the friend how a patch to the Autopilot software affected its performance and made the Model X veer, the lawyer’s response said.

The full NTSB is scheduled to hold a hearing on the crash on Feb. 25. At that time, the board will determine a cause and make safety recommendations.