Can you tell if it made from organic or inorganic material? Though this isn't too likely, it could be something a feeder ate that it shouldn't have, or even something the snake found and ate.
If it is undigested rodent parts, I had this issue recently in a rainbow boa -- passing undigested fur and bones. After it happened a few times running, I got it checked by a vet to rule out anything obvious, and when that came up negative a few doses of Nutribac completely ended the issue.
I agree that monitoring for now is the best advice.