DD (3.1) has been out of nappies for 3 weeks now. It's been a bit of a battle (but improving) with pees, but she's always been perfect at poos from day 1 and we've not had a single poo accident. But today she's pooed in her pants twice. She doesn't seem to have an upset tummy, or any reason for this. She seems totally unperturbed by it, and hasn't told me after it has happened (until I've noticed the smell and asked her directly).
Any ideas why this might be happening, or what we can do to stop it happening?