Housebreaking my Yorkies

I have two Yorkies under the age of 6 months who are totally housebroke with a doggie door. But, every night (they sleep with me) one of them poops next to my bed on the carpet. I didn't know which one was doing it and they both can go out their doggie door at night as it's open.

I solved the problem by taking a bunch of unwashed clothes out of my clothes hamper and laying them all over my carpet in the bedroom. I figured neither of them would DARE poop on my clothes. And, Viola, it worked! Four days have gone by now and I've woke up to no droppings on my bedroom carpet.

How strange! And what a creative way to stop the behaviour. I wonder why one of them was doing it in the first place? Afraid of going outside alone at night maybe?

ohhhh i love yorkies.