My dogs sleep in their crates by their own choice. The door is open yet they sleep in there all night long or even during the day if I'm out.
As far as potty training, I have a feeling that it is not that he doesn't know where to go. I believe it is more that he can't help it. If he hasn't done this in months it means he knows what the doggie door is for. They don't just all of a sudden forget that they pee/poop outside... it comes to a point where it is instinctive and him showing that he knew he was doing something wrong yet can't help it further shows that he can't help it for some reason. Peeing and pooping both? That is not a good sign. Was his poop normal? Or was that soft poop?
Something is wrong and I don't think the crate is your solution in this situation. The vet might be able to give you insights on what could be wrong.