Hi, I was going to fill a SR after I just ran into this situation.
I have just set up a Veeam backup infrastructure and The exact same problem appear randomly after a backup ( so a snapshot ) on my 2012 efi vm, they can't boot anymore since nvram file get corrupted. i must delete it and let esx host recreate it. So the surebackup is effectively inoperant cause backuped vm can't boot whithout manual modification.
have you got any update about this issue now ?
regards,
edit.
My 2008r2 vm seems unaffected though