Most kites I've flown will do that when they're so overpowered something has to give. That usually happens as I swing it for a boost though, not mid-boost, or if I'm cruising along happily overpowered and then a gust takes it to the next level of stupidly overpowered. Could be a combination of pressure and overpoweredness, ie there's enough pressure for a stable wing at normal power but not at overpower.
Yes I am too fat...