I agree that they have a poop schedule and you'll need to figure it out.
Bailey is a once-a-day pooper - usually in the evening. I don't relax until she's done her business. She knows the difference between "go potty" and "go poop".
In fact, just tonight, she hadn't done her business yet - so we went to the back yard. Bailey didn't want to go because she was still working on her bully stick. But I made her leave it in the house and we went outside. She quickly pee'd and wanted to come back in -but I said "gotta poop?" and yep, she ran off to poop (I scooped it up) - and then we went back in the house. She's still working on that bully stick.
I'd say - that if they are pooping in the house, then they are not fully potty trained. Keep their area small, block all hiding places, watch 'em and continue training. They're smart and will learn if you're consistient and catch them in the act and then correct their mistakes.
Good luck!