Followup. Took the 150 to another dealer who was already a Kymco ATV dealer and took on the scooter line recently. I told him what I've read about defective CDI units, etc. Called me a few days ago. Said he put it on a stand and let it run. After 20 minutes, it just quit dead. He immediately checked for spark and there was none. Turned the key off and on again, had spark. He called his Kymco tech who scratched his head but said he supposed it was possible.
Apparently there's no aftermarket CDI (other than the derestricted unit) and my scooter is still under warranty so hopefully that's covered. I'm hoping the replacement solves the problem.
I love the scooter but quitting dead with traffic behind me is not my idea of fun.
Hope this helps someone else.