Drive 51 freezes at "Software Loading"

No I sit patiently... also note that when trying to update system software it prompts for step 1, but after completing Step one, then unplugging and replugging (as instructed), the step 2 of 2 window displays momentarily, then cycles back to back to the update window.

I don’t own a Drive 51 but I’m puzzled by your wording of “…unplugging and replugging (as instructed.”  I don’t ever remember getting an instruction like that with my three devices.

Windows occasionally has issues with mtp devices, I'd try setting your device to mass storage mode.

I recently helped my brother in law to get his newly purchased Garmin Drive 53 up to date with the latest map and software updated. On his device I also for the first time saw the "unplugging and replugging" instructions. Maybe it's Garmin's new way of updating their devices. 

Another thought: you would not have Google Drive client installed on your PC by any chance?

I found that it's interfering with GE and I need to disable / turn it off when I connect some Garmin devices to PC/GE - otherwise they connect/disconnect all the time.

Thanks for taking a stab at this but...
The problems remain; a frozen screen on startup with the message "Software Loading..."; the failure to commence the second step of the Garmin Express update routine. 
When attempting to solve the issue, I've ensured that the Garmin device and MicroSD are recognized and accessible when connected to the computer, Admin priveleges on the computer are in effect, a fresh copy of the Garmin driver and Garmin Express are used, and direct DSL and WiFi have alternately been used during the attempt to solve the problems. 
I have also tried (1 at a time), 2 different cables. different USB ports (2 USB-A, 1 USB-C)
I've included the step windows from start to recycling.