Smell of decomposition and no answers- any help appreciated

This is both a tale and kind of gross. Please bear with me.

8 days ago- we notice a “poopy” smell in the kitchen. We have a one year old baby and the kitchen is where we dispose of diapers, and we had fallen behind on dishes by 2-3 days due to everyone (3 adults + baby) getting flu at the same time, so we clean the kitchen and dishes, bleach the garbage cans, and sanitize the sink and dishwasher. Oops, lesson learned, right?

7 days ago- poopy smell back and stronger. Turning on the heat seemed to make it worse. We run oxiclean through the dishwasher and draino the drains, thinking food got stuck somewhere? Trash cans removed and bleached. Fridge scrubbed. Baseboards scrubbed. Oven scrubbed. By “scrubbed” I mean “obsessively emptied and cleaned with heavy duty cleaning agents, as opposed to everyday cleaning spray like a normal weekly clean”.

6 days ago- a plumber comes out and we clean out the drain pipes, pipes under the sink, and garbage disposal. At this point I have WEIRDLY clean appliances and pipes.

5 days ago- we send the man of the house into the vents in the basement directly below the kitchen. There is no smell in the basement. The basement is 1/2 the homes living space and fully finished. We find nothing in the vents. There is some evidence of mouse droppings beneath the kitchen sink, but no one is certain it’s mouse shit and not just like… dirt. We did have an infestation a year ago, but we cleaned after that.

4 days ago- we have two specialists out to scope both the vents and the pipes. All clear. We are assuming it is a dead animal somewhere. No pest control nearby nor animal control can/will help. We rip the cabinets out of the walls and find some weird shit previous owners left behind, but no corpses or rotting piles of mold or whatever is making the smell

2 days ago- we check the attic. The attic is not actually accessible to humans. Non starter. But what we did see peeking in is nothing. No smell up there, either. Animal control is confident (via phone) that that’s not the problem zone.

Yesterday- we punch a bunch of holes in the walls around the kitchen, trying to localize smell. We cannot, beyond “near dishwasher”. We order an endoscope. No pest control will help us, because they won’t find/remove dead animals, and that’s what I am still assuming this is at this point.

Today- we think we see a dead rat with an endoscope. Drill access holes in floors, wall, and cabinets. The smell gets much much worse. It is a piece of fuzz we end up finding.

We do find some black ichor behind the dishwasher that is new from the last time we removed the dishwasher (day 6).

The house is unlivable. I write you from my mother’s basement, where we are all crowded in. If anyone has ANY ideas, please help me. Anything at all.

The smell is VILE. It smells like decomposition mixed with human shit. It gets worse when the heat kicks on. It gets worse when the oven or stove is on. It gets better only if we air the whole house with fans pointing out of the kitchen. It is not anywhere except the kitchen, but it is PUNGENT.

The house was built in the mid 70s.

UPDATE 3/5/25

It was the fridge-freezer combo. About a month ago I was trying to put a ninja creami base in the freezer and dropped it, splashing the whole 2.5 cups of protein powder and liquid down the back of the freezer. At the time I removed everything from the freezer and scrubbed the walls, but it ALSO poured into some kind of drain pipe(?) in the back. I didn’t notice at the time. Didn’t even know freezers HAD a tube/pipe thing in the back. Regardless, it apparently rotted in there, then started to leak out onto the tray under the fridge.

We are unsure if a mouse also got into the pipe and died, but removing the pipe, bleaching it, removing the tray under the fridge and bleaching THAT as well seems to have resolved the smell. Rotting milk and protein powder is disgusting!