that is an interesting observation about B12. I had sleep issues at the beginning, but years later I do not.
I haven't been able to zero in on what made things shift, but B12 would make sense. I had been severely depleted back then, and now I am not. In fact a recent blood test even shows B12 to be slightly high! (After supplementing, trying different types, for YEARS!)
I also take ZenMind (which is GABA) at night. I sleep hard almost every night. Never wake refreshed - but I sleep like I'm comatose!