I also just did the update to 1.10. It was an update from hell experience. After the first failed attempt the camera showed the red light next to the C4 button. After that it took me 4 more failed attempts, with removing device, switching camera off, removing the battery, and reconnecting the USB before it finally succeeded.
What I did notice is that somewhere during the process the USB connection to the camera on my win10 pc switched from storage to sony device. And I could not remove the usb connection through the 'Safely Remove', but from the 'devices and printers' control panel.
I recently did the 1.10 update to my A7RIII, the same day I received it.
I'd read horror stories about failed Sony firmware flashes, and had a PC motherboard fail during a BIOS flash many years ago, so I was nervous indeed. But I followed the instructions with fanatical care, and everything went smoothly.
Then I allowed myself a deep sigh of relief.

I hope I don't have to do that again any time soon--I doubt I'll ever be comfortable with that procedure.