Tesla did not immediately respond to requests for comment outside regular U.S. business hours.
The release of the new driving assist system to some owners of Tesla models, which the company said featured several improvements, had been announced for Friday, Oct 22.
On Saturday, Musk said the release would probably be delayed by a day. "Regression in some left turns at traffic lights found by internal QA in 10.3. Fix in work, probably releasing tomorrow," he tweeted on Saturday.
The Tesla vehicles with the latest 10.3 software repeatedly provided Forward Collision Warnings when there was no immediate danger, according to video postings of beta users. Some vehicles also automatically applied brakes without reason, users said on social media posts.
Some users said they lost the FSD beta software entirely after having problems with the latest iteration.
There was no information on Sunday about a possible new date for the release, either from Musk on social media or from Tesla.
The National Highway Traffic Safety Administration (NHTSA) in August opened a formal safety probe into Tesla's Autopilot system in 765,000 U.S. vehicles after a series of crashes involving Tesla models and emergency vehicles.
A NHTSA spokesperson on Monday said the agency is aware of reported changes to Tesla’s advanced driver-assistance system and that it has contacted Tesla for more information.