A few years ago my cats and dogs never ate on their own or pooped...
I thought it was a bug, but it turned out to be caused by a mod, that fullfilled the needs of my animals everytime I loaded the game or the family.
If the poop bothers you that much, you could try to put the mod in your game.
It's called "No Sick, Dirty, Sad and Hungry Cats & Dogs" by LittleMissSam.
In the description it says:
"Disable Decay Prevenger Buff for owned Pets:
When loading a Household the Part of the Mod which adds a hidden Buff which decreases the Decay of Needs will be disabled"
So technically your dogs will never poop again if you download this part of the mod (if I understood this correctly. English is not my first language). But this also means that your pets are never hungry or sick. If I remember correctly you can still call them to eat manually, they will take a few bites and stop to eat.
Maybe this mod will help you with your problem and you can enjoy your game with the furry friends. :)