Crash disarm in flight

On a checked and tuned octocopter, we faced a new problem. Crash disarm and fall. Occurred 2 times in a row during smooth flight, approximately 3 minutes after takeoff. After the first crash, I disabled the FS crash check - value 0. BUT it did not help and today there was a second fall of the octocopter. Attached are flight logs 1 and 2, both with a fall for this reason, I ask for help49 07.10.2020 15-25-18.bin (1.9 MB) 2020-10-06 13-42-07.bin (2 MB)

Did it suddenly fall from the air? Was there any obstacles around?
What I see from the log is the copter shut its rcin and rcout. It was following the desired altitude quite nicely. Power was still connecting.

Both flights in the field, without hindrances and obstacles

Watch the video of the second flight