Not sure what you mean. If autopilot has a bug then there is a good chance a lot of other cars do too, since (afaik) autopilot is not at its core Tesla proprietary tech like FSD.
If the end user said they were driving on FSD, it likely means they are enrolled in the FSD beta and were using autopilot - in the car there is no distinction between autopilot and FSD. They are the same thing in the car if the FSD beta is enabled.