Crisping Butternut Squash Chips
You can try slicing it thinner (about 1mm or less, like a normal potato crisp), to further increase surface ratio in your crisps and make them dehydrate quicker and fully in the oven, so there is no moisture to migrate. 

The difference between frying and baking is how your food is exposed to heat - frying is sudden exposure to high heat that leads to dehydration of the surface of your food and makes it crispy. This doesn't last long because then the moisture at the core of the food migrates to the surface and makes it soggy (like french fries and chicken nuggets). Unless your food lost completely all the remaining moisture and it doesn't migrate to the surface (like happens with potato crisps). 

Cutting your squash as thinly as possible might be the solution to have crisps, so your oven can fully dehydrate them and you don't have the leathery texture.