UNO WiFi Rev 2 Power Problem

What Works:
I purchased 2 Arduino UNO WiFi Rev 2 units from Amazon. The boards both work great when they are powered by the USB port. I am able to upload sketches and run them with ALL functionality including WiFi connectivity.

PROBLEM:
However when I plug in any 9-12 volt supply I routinely use with other Arduino board models, the UNO WiFi Rev 2 boards will not function. The green onboard power LED lights, the WiFi will not connect and the USB connection to my development computer running the IDE Serial Monitor is dropped. The board is in some state where it must be power cycled to restore operation.

BTW, I measure no change in the 3.3VDC and 5VDC voltages on the power header when I plug in the external power supply. `

I am concerned that these boards either were not tested or I have had two infant mortality failures in the power circuitry.

Anyone else experience this issue?