We have a quad of about 10kg that lately was updated to 4.1. We kept all the old settings and rerun an autotune and it flies really well. >One problem popped up tough, about every other arm it disarm instantly. I have to arm it 2-3 times before it stays armed and lets me takeoff. No errors show up. >Any hint to where to look?
It could be that a terrain failsafe is triggering. So perhaps you’re attempting a takeoff in Auto with the takeoff altitude set to terrain but the rangefinder is out-of-range (sometimes). This is a guess of course.