Performed a inspection today and found odd looking substance in probably 90% of the receptacles. It was always in the bottom grounding hole of the three prong receptacle. It was dark brown and appeared to have be fluid enough to run down the receptacle a short distance. My first thought was some type of insect but I don’t know why they would only enter the grounding port. Has anyone see or heard of this? See attached photos. Thanks for any information.