I have a few ball pythons that will randomly stop eating rats at some point but will nail a mouse before it even hits the floor. I try similar sized rats but no go. Then out of the blue will just start eating rats again.
I know snakes can be picky just like humans I just wish it made more sense. Whats odd is 99% of my normals will always take a rat. If I have a morph they seem to think their special or something. It usually happens when they hit about 800 grams or so. I am sure others have similar experiences.