Hi Eccman:
I was wondering if you know the history of your home, is it an older home, or any reason to think it would be haunted? Just because whatever this presence is, turned on the microwave and the water in the bathroom, doesn't mean it's not the grandmother. Does your wife get "scared" or have a feeling of this being a malevolent presence? Try taking some pics around the house, especially when something like this happens. If your wife or son is uncomfy with it, try simply asking it to leave. Also, would you have any reason to suspect that the grandmother did not cross over? Or maybe, she did and is just visiting now and then, letting yall know she's there. =) I remember responding to your post about the dream you had. I still think that was astral travel, and perhaps the grandmother accompanied you on your return, to help you back into your physical body. Sounds to me like she crossed over, but is visiting at times. Something to think about...
Hugs,
Pate