Somewhat related to this thread re DD focussing error at the start of a mission (it would return to home).
Latest iPad and DD software
Flying in desert climate (45C in shade)
SD card: San Disk Extreme Pro (formatted in Go4 in device) 128GB
Flying offline (remote)
It took a bit to troubleshoot. At the beginning thought related to offline flight. Reason being I had newly bought 2 SanDisk extreme Pro SD cards for the trip. And I’d tested them prior to the trip in the park and no error. The error of focusing would pop up after some autonomous flights. The drone would fly to the start, then after taking the first pic, error msg and then RTH. Others had suggested replacing / reformatting the SD card. So what we did was replace one card with another which gave the same problem which threw us of the trail of being SD card related. Fortunately I had brought with me additional SD cards and after I must admit ‘giving up’ and flying ,manually, I swapped the SD card for a RUGGED Pro master 64GB and presto, problem solved during autonomous flights. Maybe it was the hot environment but mental note to self to check if the focus is simply related to the read/write nature, size, or brand of SD card. Hopefully someone out there might be able to shine a more technical reason for the difference in read/write SD behavior I experienced to avoid it happening next time.