A good percentage of the time if this is found after a fresh trans is installed you will get remnants from inside the trans cooler, it will flush right to the pan.
You can blow as much air in the cooler as you want,it will not flush this **** out until either a good amount of solvent and or fresh trnas fluid runs through it.
Half the time this is a cause for a fresh trnas to have instant problems tha get blamed on the tranny builder