if spot cleaning daily there shouldn't be any foul smell.
The only time my dragon cage smells is right after she poops and maybe an hour after I clean it. Most times she's only pooped a short time before I clean it up.
If the poop is in the cage for a long time and your dragon ends up burying half of it in the sand, that may be why you still have odor even after you clean up what you can find. This is one reason I don't like using children's play sand. Some people have no issue with odors with it but others have plenty of issue.
Maybe just swap out the same completely, use tile, non stick shelf liner, plastic table cloth, paper towel or newsprint instead.
-----
PHLdyPayne