So I brought it in to the dealer yesterday. They said they had only seen this issue once before. Basically, I was told what a couple people here on the forum said - that the mechanism behind that plug had too much grease or the heat here in AZ liquified it and it was dripping through the access plug. The plug pulls out easily and he stuck his finger in there and it was covered in grease/oil when he pulled it out. They said they had no other suggestions than to clean it out a bit, clean the oil stain from the top and keep an eye on it. No charge and it looks like new. Mystery solved.