Tesla is the target of yet another federal safety probe, the fourth currently open by the National Highway Traffic Safety Administration's Office of Defects Investigation. Today's trouble concerns the automaker's "Smart Summon" and "Actually Smart Summon" features, which allow Tesla drivers to remotely control their vehicles via a smartphone app.

At least in theory, that is. In practice, NHTSA says it's aware of multiple crash allegations "where the user had too little reaction time to avoid a crash, either with the available line of sight or releasing the phone app button, which stops the vehicle’s movement."

Worse yet, Tesla has failed to report any of these incidents to the safety regulator, which has a standing general order that requires any automaker or operator of autonomous or partially automated vehicles to report crashes involving such systems that occur on publicly accessible roads.

NHTSA's ODI says it has received one complaint of a crash using "Actually Smart Summon" and has reviewed reports of at least three more cases. In all four incidents, the Teslas being remotely operated failed to detect the parked cars or bollards they crashed into.

Another 12 complaints concern "Smart Summon," a less-advanced version of the same system. In these cases, as with the others, there was not enough time for whoever was operating the Tesla smartphone app to react in time to prevent the crashes.

NHTSA ODI says its preliminary investigation will evaluate the system's capabilities, including the top speed allowed when being remotely operated, as well as other design restrictions. More than 2.5 million Teslas are equipped with this feature.