It has happened to me once, too. Since then I am mindful of where the wind is coming from. Also, in my incident, thermic issues may have played a role, as it was on the shores of a lake, a promenade walk-way.
I have couple of hypothesis:
1. As someone else has told you, props in wrong arms.
2. Wind is too strong
3. The arms of one side of the drone spin faster than the ones on the other side.
4. Software problem
Contact GoPro official support for more information or to discuss this issue
When taking off, just tap the screen, and keep your fingers clear of the controls and let it hover. What I suspected happened was the sideways control was knocked over sharply causing the two port or starboard motors to rev and flip the drone.