Alexmos fried, why?

I've been through two 8bit alexmos boards now. I'm getting ready to buy my third, but I really need to make sure I don't break this one.
The first board I purchased worked fine for awhile (2-3 weeks). Long enough for me to learn how to tune it at least. Then one day the Yaw ext stopped working. I finally gave up and ordered a new board. The new board worked fine too. then after a few days it stopped recognizing the sensor. I plugged the sensor into the original board and it worked fine.
I'm powering off of a 3s. Am I doing something wrong? Am I frying these boards? It seems odd that two would be defective.
Please help. I've been working on this ariel camera platform for a year now. It's been a learning adventure, but this is the home stretch. I've managed to get everything working the way I want then my boards die.