Started feeding 9 month lab in crate, why does he poop in crate immediately after?

I recently started to feed my lab in his crate due to him feeling intimidated by my cats while he eats, so now whenever he finishes eating he immediately poops afterwards. I take him out to go before he eats, as I like to let him rest for 45 minutes after eating to digest. He has a rather sensitive stomach and gets diarrhea regularly so I’m used to him going in his crate when he gets those bouts. Could there be a reason he’s doing it, as in it being territorial, or is it time to visit the vet for some tests to rule out any serious issues?