No you don't have to Mount system. That's was probably the issue the whole time. Updater takes care of all that $3π+ £®m€ ×X× ®∆z® |/|@xX Π¶ oπ $ø|/|£ťhïñğ ¢ű$ț¤|/|
Hi guys - I have success doing the mount and not doing it. I'm not sure what base Rage has - it is a kick rear end ROM, no doubt. But it is one of the few (Validus being another) that I've had issue with from time to time going back and forth. Not sure it will add any value, but here's exactly what I do when I'm not sure about the start or end point (i.e. something like Rage)
Boot into twrp.
backup nandroid immediately
mount system
wipe - advanced - everything BUT internal / external storage.
back out, then Factory Reset (yes, I know, shouldn't matter)
go back in, then wipe - advanced everything BUT internal / external storage again (yes, I know............)
back out to main menu
be sure system is still mounted
install - pick ROM and pick correct GApps. Install
Reboot
I have no idea if this is true or not - but I believe the base (i.e. system?) must be completely killed when going up or down. And I also believe mounting system is required to do that.
Again - i may be smoking dope here - but based on what has worked for me, this is the conclusion I've drawn.
Hope this helps.
BTW - can we assume you are unlocked?