Rich,
Yes, thanks for the heads up. This is an embedded system where the Pi power is supplied via the GPIO pins. It's been working well for several years. Maybe only marginally working

. I don't think we've ever actually monitored the voltage drop across the GPIO pins.
So we've got some work to do. The test setup I've been using to solve this problem has a 40-wide flat cable that is probably twice as long as the one in the actual product. Hopefully this is the issue. TBD.