2012 MBP weirdness

[dirtybeatfreak]

Well. I thought about resetting the NVRAM, but its a fresh install. Surely NVRAM is for caching your settings? Of which i had none.
NVRAM is the updated version of PRAM no?

Yep, they're pretty much the same thing. It resets things like volumes, res, time zones. But it will also disable verbose mode. This is of course an assumption that it is verbose mode that you're seeing, I'm not really sure what else you would mean by Log utility or do you mean it auto boots to the recovery console (same screen if you hold cmd and r)??

 

[Banzai_Joe]

Good morning.
So i reset the nvram and this is what happens.
Apple logo comes up, progress bar gets about 50% through, then the progress bar restarts from the beginning, gets about 10% through then gets to a window that says "The macOS installation couldn't be completed" then some bs about looking at installation log (which is on screen behind the window) to help diagnose the issue. I then have options to shut down, restart, save log or view log.
The apple menu gives me the option to to choose startup disk, restart or shutdown. Choosing startup disk does actually show my ssd with HS 10.13.6 on it, so i select it and restart.
Bugger me...........it boots!
'Restarting' works too.
Shut down and cold boot up.........and it works!
So, it looks like i might be a genius.......for following dirtybeakfreak's genius advice.
I'm not utterly convinced its fully fixed, but i'll see how it goes for a few days.

Thanks fellas, your advice has been very much appreciated.