Thanks all. Told him what zombie said, about the pencil, nail, whatever. Soon after, got a call saying it was fixed. I asked what the problem was, and he said he adjusted something, not sure what it was. I was thinking about buying a larger scooter, or maybe an older trike, but couldn't sell this one with the vibrations, so this frees me up. Now, to convince my wife I need a bigger one.
Thanks again for all the great suggestions. I think those responses were on the money.