Getting crispy banana chips My pan fried banana chips are crisp at the beginning.But later it looses crispines.This happens evenafter storing in air tight containers.What is the mistake i am making?

PS:I am asking about kerala(indian state) style famous banana chips.It is made from only a certain variety of banana available here. Usually made after chopping raw bananas in thin round slices,adding turmeric powder with salt and then deep frying.
The raw chips should be sliced directly into the hot oil for deep frying. The frying oil should not be too hot. Further the deep frying should be done on medium heat till all the moisture in the banana chips are completely evaporated. The oil should be pure coconut oil. After removal from the pan the deep fried chips should be stored in air tight plastic covers to prevent moisture regain.