My snake developed an RI; from what I've read (a lot) I'd add stress to that list. His husbandry with me is fine. He came from a neglectful environment but had no signs of illness when I got him, and that was a couple of months ago. He's my only snake. However, something very, very stressful happened to him recently and he came down with an RI about two days later. I don't think it's unrelated; there is no other reason I can think of.