Did you clean off the items in the cage (hides, water dish, decor, etc.)? Sometimes the items will still have that crap-smell to them so it's always important to wash off the cage items so your cage doesn't end up smelling.

Also, when your snake defecates, do you clean up the feces and a bit of the area around it? Spot cleaning would be very important to do so your cage doesn't end up smelling and your snake doesn't end up slithering through the feces.