There are several things about this incident that suggest that it was caused by geomagnetically distorted launch site. Probably because the pier under structure contained steel which was then close to the MP…
At -23 secs the MP went from reasonable values of magMod and Yaw-magYaw to problematic values - I’m betting this is when the MP was placed on the pier in preparation for launch.
Also, the pink background indicates that the MP never switched to GPS_ATTI.
Another indication of a compromised compass is the flight path
These observations and a few others all point to a geomagnetically distorted launch site. But, the MP was in ATTI (not GPS_ATTI) and should have been impervious to an incorrect compass. I.e. it’s only GPS_ATTI mode where erratic flight can be caused by the Flight Controller attempting to correct position based on incorrect compass data.
That said I still think this incident would not have occurred if the launch was delayed until the controller indicated that GPS_ATTI mode was in effect.