OTHER VERSION Opensuse 42.3 decides not to boot then I can't upgrade " filesystem snapshot could not be created"

Hello,
My main Opensuse 42.3 system crashed and then decided it won't boot for some reason:
Boot log:






I have no idea what's going on here - any suggestions on how to debug it very welcome.



Anyway I decided it would be a good idea to do an upgrade.

So I ran the CD upgrade to 15.0 and I get this





Filesystem snapshot could not be created.


I then booted into the 15.0 rescue console and found I can mount the / partition OK

mount /dev/sdb2 /mnt

btrfs scrub start /mnt
brtfs scrub status /mnt

seem OK

cd /mnt
and my root partition seems OK

I can see my etc at /mnt/etc and it looks OK on the face of it

I can't find any logs in /mnt/var/log however


So any suggestions on either how to fix my 42.3 or why the 15.0 upgrade won't work are very welcome
Many thanks

Images at
https://imgur.com/a/OoYZFMH