I would beef up the ground electrode system and be sure all of the connections are tight.
It is not unusual that the "neutral" from the utility is not really "ground".
The only fix is to try to be sure "ground" is as close to earth potential as you can at the home.
I would certainly start by checking the ground clamps on the rods. I was getting bit when I first moved in here and I made it a whole lot better, just by replacing the clamps.
