Government UAS Pilot reported the UAS battery system attempted a reboot mid-flight causing a power loss to the motors; resulting in the UAS crashing.

Narrative

On Day 0 at approximately XA00 hours local time Pilot [person manipulating the controls] was providing an overwatch stream for a unit.While on station at approximately 394' AGL Pilot experience a signal loss warning on his Ground Control Station (GCS). At the time the system was approximately 1500' from the GCS and connected via the native SL connect for both control and video. When he looked up the UAS was no longer observable. After the scene was secured he proceeded to the last reported GPS position and located the UAS in an open field. No injury or damage was reported beyond the airframe itself. During the debrief forward VOs state that they saw the anti-collision strobes stop and solid blue lights (Standby Indicator Lights) come on the aircraft as it descended. A review of the logs by the manufacturer revealed that there was a battery control board software issue that he initiated a restart mid-flight cutting power to the motors and causing the failure. System replaced by manufacturer. ***Related to [previous] incident with systems*** (Same defect.)At the time of the incident this airframe had several dozen flights totaling XX.XX air hours. All proper pre-flight procedures had been conducted. After interview and debrief there were no adjustments to CRM or policy that could mitigate future risks.