SparkFun Adjustable LiPo Charger PRT-14380 Board Burnout?

We have several customers that are having the SparkFun Adjustable LiPo Charger PRT-14380 suddenly stop working after a few charges. They are charging 400mAh and 850mAh batteries. Another vendor who uses these has seen them burning out if they are charged using the 400-500 range option. Has anyone else experienced this? It seems like maybe this batch of boards isn’t working properly.