Problem with booting vero

I have this situation where it sometimes fails to boot.
As far as I can tell, this is purely a problem with a poor connection of the power lead - since it seems to clear (but not reliably so) when unplugged and replugged.
I’d like to know whether there are any reliable indicators (in the form of lights?) by which I can tell whether it is failing?
I can sometimes see a glow through the spdif port (if that is what the hole with a flap is), and I think I see a correlation with this coming on and then extinguishing after a few seconds and the box booting.
I should explain that my colour vision is ‘wonky’ - I have a marked red deficiency in my vision, which renders a band of frequencies far less visible.
Derek

Hi

The light SPDIF should be on when you power up, and go on after a few seconds. This indicates that the bootloader code has been read and the boot process is initiated. If it stays on then the bootloader has not been read. You may have some luck reseating the SD card.

Sam

So far, I’ve almost never had to reseat a card, except after I’ve changed to a different one. The problem is ‘cured’ by unplugging or wiggling the power cord into the vero and then powering on, strongly suggesting a problem with the seating.
Derek