Can someone please help me with my shih poo puppy?

I have an almost 6month old shih poo puppy First three weeks he was doing great with crate training and not having any issues with the crate. Then all of a sudden he started pooping and peeing in his crate. And this started happening everyday. I use Nature's Miracle and other enzyme cleaning products to clean his crate. The crate is only small enough for him to stand, turn around and lay down. Nothing in his schedule has changed nor has his food changed. Idk what else to do. I am thinking it might have to do with separation anxiety but idk how I can help him with that when we are away. But I also am not 100% sure that's what it is. We are away from the house for about 7hrs a day and we have a neighbor come and take him out in the middle of the day and he will have poop and/or pee in his crate when I come home. Idk what else to do. Please help!