Everytime I see a post like this I have to laugh. I was in the same boat with one of mine. Oh my gosh how disgusting I thought. How could one of my yorkie babies being doing this. LOL
I tried everything from the forbid, pineapple, to the meat tenderizer. Nothing worked for mine except for growing out of it. Apparently, the variety of 5/6 star foods is just so good, sometimes they want to re-eat it.
Most really do just grow out of it.
I would keep it picked up as often as possible. As they get older, they poop less and on more of a schedule so its easier to grab before they have a chance to get to it.
At 4 months old...pups are just interested in everything