Well maybe it DID finish flashing, HOWEVER, upon restarting I can not access the gui at all.
The web browser never registered a response from the unit so the page showed "flashing" even after the unit had restarted itself (and stopped working).
Rare problems occurring seem to be what happens to me. Wish there was a way to re set it. Holding that reset button does nothing.
You are now raising the possiblility that you have not bricked the board ... do you have any other S3+'s on your network and if so is any of them on the default static IP?
When you flash a unit that (usually) is on DHCP, th web UI will NOT register a response because the flashing resets the IP to the default one and turns the network settings to static. Thus you have to log onto the default static IP (192.168.1.99) rather than the on you had on DHCP. And if you have 2 units on the default IP, ofcourse one will not show up on your network, and that will be the last to ry to use that IP (which in this case is the rebooting / reflashed rig).