For anyone else in the future:
I still got no log entries from the above thing, but I’m sure the power supply was the issue.
Despite it still providing enough power to keep the light on the optical out going, I think it slightly dropped in voltage which froze the Vero.
I tested with a 4.5V supply and it behaved the same (works for a while, then all of a sudden freeze).
After changing to a new 5V power supply I have not had a freeze in 3 days (whereas before at the end it happened after a few minutes consistently).
So if you have an issue, do try a new power supply, 5.5mm outer diameter, 2.1mm inner, positive center, 5V, at least 2A (taken from Vero 4K Power adapter specifications - #8 by sam_nazarko )
The one I bought is from Deltaco, but I know it can be bought from the OSMC store as well (can’t find the link currently, but search the forums).