My puppy won’t stop pooping in his crate

Hi, I have an almost 6 month old Jack Russell beagle mix puppy, and crate training him has been very tough for me. I live with my brother and my sister-in-law who both work, and so do I. My sister-in-law works just downstairs, and my brother and I work farther away, so my sister-in-law tries to come upstairs and let him out during her shift if she can, but every time she does, he’s already pooped in his crate. I always make sure he either poops the night before, or in the morning before I leave, but it doesn’t seem to help. I used to feed him in the morning, and again when I got home, but I’ve now had to stop feeding him in the mornings. It worked for a few days, but he started pooping again, and I’m unsure what to do. I’ve tried making his crate smaller, but that didn’t work either. Is there anything I can do to stop this behavior? Or will I have to ride it out until he’s a little older?