Probably a battery connection caused by the battery not being inserted completely. A 1mm gap where the battery head hits the housing of the P3 will cause this-- Several instances on the forum threads relating to this issue.. It happened to me once -- so I check every time to make sure that it is all the way in. the P3 housing.
I thought I did too-- and there is always the possibility of the latch on the battery being defective-- that has happened also.I always check.
Same thing happened to me at 47%, but I was above a tree at about 40" and I was able to steer it into a open area and it landed safely. I never I these issues till after the last firmware upgrade