When starting up the motors if it fails to start right away after holding the RED button for a few seconds and instead emits a tone, do NOT keep trying! I think it's better to power cycle the H and try again. Started with doing a full preflight check, double checking each prop was on securely, H was initialized, etc. Noticed the motors didn't start up on my first attempt, so I simply thought I must have let go of the red button a tad early. Tried again a second time, same thing, after 3 seconds instead of spinning up the H would just emit a short tone. Tried it once more and on the third time it spun up as normal. HOWEVER shortly after lifting up noticed the bird was squiggly so tried to immediately land it. I was able to touch down on the ground briefly, but instead of the props spinning down like normal, it suddenly went full speed backwards (towards me!) dragging along the ground. Obstacle avoidance was off, was in angle mode. Broke 3 props. Was able to test the H after the mishap and got a full flight with perfect hovering, flying, landing, etc, so have no idea what happened other than something glitched. So word of caution: if the motors don't spin up right away and instead the H emits a tone in response, don't keep trying. Reboot it!