You are correct Butters. It was a case of a flattened truck battery and then the LiPol battery in the Garmin and not after any updates or other circumstances. It also began Bootlooping immediately upon reconnection to USB power. It continually loops with no other words other than the Garmin logo.

However... It now will power itself off and remain off after the last flash attempts that were successful, so long as it is not connected to USB power as well. Connecting once more to USB continues a loop unless I hold the power button. This will cause the Garmin logo to remain after one loop until I release the button. The unit will then continue looping until I pull the USB where it will loop once more and shut off, so it seems there has been some kind of progress.

It is regrettable they have chosen to use substandard chips in such needed and valuable devices, but that seems to be the way of many companies in this era.

My last flash attempt was using the original firmware via the updater.. so here's hoping. I am definitely willing to continue until we determine whether or not the unit has died or is still usable.

How shall we proceed?