XPS13 9370 no hard drive at boot only if power plugged in

I've got a 9370 I've had for over a year now.  All firmware and drivers current.

I've had random issues for the last year with a power on giving me a white screen saying no drive found.  And it literally isn't, I can go into the BIOS and look through settings and there is no hard drive installed.  Since this is a 1 TB SSD soldered to the system board, it's not like I could wiggle the cable or reseat it or anything.

I had set up a trip to depot for it under warranty, but literally 15 minutes after that phone call with support a new firmware for the drive came up.  I tried it, and when the problem didn't repeat, I let the case lapse.

Then it started happening again.  I finally tied it down to one specific thing - if I have a power cord plugged in when I turn it on, it will not see the hard drive.  Since at home where it always happened, I have a non dell USB power cord from when I had my HP Spectre X360, I thought maybe it was the non Dell power cable.  So I was getting set to buy another OEM power cable for this, and decided to just use the one I keep in the laptop case that came with this, at home, and use the non standard one for when I'm at a client and need to plug in, since I'm always already powered on at those locations, just need to juice up the battery.

Lo and behold, even with the original Dell power supply that came with this, same thing happens.

Anyone else ever see this?  I'm seeing a lot of errors in the forums with drives not found, but it seems invariably to be other things.  I've not seen another thread where it happens EVERY TIME if power is applied, and NEVER if power is NOT applied. 

As soon as it starts the spinning dots showing Windows loading, I can plug in and be fine.  I just can't be plugged in at the initial period of a cold power on.

Thanks for any info.

John