Musk is in trouble again. Tesla and the billionaire are being sued by the company's shareholders.

A proposed class action lawsuit was filed Monday evening over the first public test of Tesla's robot taxi in late June.

Tests showed the vehicles exceeded the speed limit, braked suddenly, hit curbs, drove into the wrong lane and dropped passengers off in the middle of a multi-lane road, Reuters reported.

Tesla's share price fell 6.1% in the two trading days after the tests began , resulting in a loss of about $68 billion in market value.

Musk and his company have been accused of repeatedly overestimating the effectiveness and prospects of autonomous driving technology , thereby inflating Tesla's financial prospects and share price, Reuters reported.

Shareholders said they believed Musk's assurances during an April 22 conference call that Tesla was "completely focused on bringing robotaxi to Austin in June," as well as Tesla's statement the same day that its approach to autonomous driving would ensure "scalable and safe deployment across regions and use cases."

The development of robot taxis is crucial for Tesla as the company grapples with falling demand for aging electric vehicles and criticism of Musk's policies, Reuters commented.

Musk wants to offer the service to half the US population by the end of the year, but he needs to convince regulators and assure the public that his technology is safe.