In the bad old days of aircraft maintenance, it wasn’t uncommon for shop personnel to fly customer aircraft as part of troubleshooting and final testing. Now insurance and liability issues generally quash the idea. The hangar keepers liability insurance policy shops carry might only cover ground ops. This often results in the shop technician flying shotgun with the aircraft owner on a test flight. I have some grey hairs from years of doing just that and will forever remember one maintenance flight that went bad: Engine failure forced a landing in a cornfield, destroying the aircraft.
Crashing on a maintenance flight can be muddy because a third party (the shop) is involved. If that shop is an FAA repair station, it might have specific flight-testing guidelines and procedures written in its ops specs, which govern the conditions under which the flight is conducted. The flight can likely only be made in VFR conditions and without passengers—a common-sense practice after major maintenance