UAS crew reported a single drone of a multi drone UAS flight had an error after launch and landed.

Narrative

Event occurred on launch of a routine 30 drone light show. One drone triggered a 'Land' command due to a probable compass anomaly. As the drone was landing; the suspected compass anomaly caused it to fly well away from the launch and recovery zone before landing. Remainder of drone light show proceeded normally with 29 drones. A detailed investigation and safety report will be completed to determine mitigation for future occurrences; however; this will serve as our preliminary report.Initial analysis shows that the Extended Kalman Filter detected a problem which triggered an automatic 'Land' command about 5 seconds into flight from 9 meters. The landing started normally but the drone started moving in random directions which interrupted the descent. The drone landed about 225 ft. away from the initial takeoff about 27 seconds after takeoffMost concerning is that the drone breached 2 independent geofences prior to landing. The drone correctly sensed and triggered 'RTL' and 'Land' commands at both geofences; but the causal problem resulted in the drone being unable to RTL and continued flight in an unintended direction before it could 'Land'.Our initial set of actions to close this report includes: Continued analysis to verify the suspected problem. Report issue to manufacturer. Pre-flight procedures to be evaluated for any techniques which could have detected this problem in advance. Note: there were no cautions or errors indicated on the control software prior to flight and the drone headings are shown graphically on a map. Ensure Red Button software window is readily available to Disarms an errant drone; decision and reaction time in this cause would have needed to be about 5-10 seconds to identify the proper drone number; locate it on a separate window; and manually disarm it. Experiment with starting the drones on a different heading to increase probability of compass anomalies causing flight toward least risk location.