Quoted from WolfManCat:
Replaced the PSU, replaced the power distribution board. Still no update.
So now is it narrowed down to the flash drive and or the SD? Can a faulty node board under the playfield cause an update to fail?
Given that Stern has been stingy with actual technical documentation on Spike for over 2 years now, despite Gomez's failed promises to release more, who knows? We're all in trial and error land.
When you imaged the new SD card, was it a NEW card, or was it something just laying around? Same size and rating as the SD card in the machine? What happened? Did it work like the other stock card, but just wouldn't update, either?
Also, when you do the update, you might want to record it with an iphone in slo-mo mode. Maybe it's flashing a message so quickly you can't see it. Playback in slomo might help yield a clue.