A potentially faulty driverless car feature found in roughly 2.6 million Tesla cars on U.S. roads highlights the risks associated with CEO Elon Musk's plans to roll out unsupervised Full Self-Driving this year.

Musk has complained that U.S. regulations are too onerous and are holding back the development of self-driving cars. Ethics experts are worried that once President-elect Donald Trump takes office, Musk will push him to ease oversight of Tesla, which just suffered its first decline in annual sales in more than a decade.

The National Highway Traffic Safety Administration has launched an investigation into crashes It said occurred while Tesla vehicles were operating with a parking feature that allows owners to summon a car from a parking space without anyone being in the vehicle.

The “Actually Smart Summon” feature enables drivers to remotely summon or move their vehicles to them or another location via a mobile phone app.

The National Highway Traffic Safety Administration is probing about 2.6 million Teslas after regulators discovered that a feature on multiple vehicle models was tied to crashes. The feature, known as "Actually Smart Summon" is intended to have the car park itself and pick up its owner using a button on the Tesla app.

The agency has previously investigated earlier versions of Smart Summon, which is meant to let a Tesla vehicle park itself or fetch a driver via remote app command.

Tesla is under investigation by the NHTSA once again, this time over the automaker's "Actually Smart Summon" feature, which allows users to recall their Tesla to their location remotely, for example across a parking lot.