Disregard Stock problem

Whenever I edit a products' sub-product and have one item checked on Disregard Stock, and then later on I make any type of change to that product, the disregard stock becomes inactive on its own, which then makes the option for that product inactive. Why? Everytime I make a change for a product I have to go and make sure that disregard stock hasn't become inactive on any of the options, it gets very tedious.