Every so often Spacemacs stops everything to ask me if I want to steal savehist from myself. I'm not entirely sure what's going on there.
Guessing you've got multiple spacemacs instances running? & they're both trying to own the same savehist file. Or at least those are the conditions under which I encounter that.
I thought it might be something like that. I am running an emacsclient off of a server, but I thought I only had one client running. Going to restart the whole thing and pay closer attention.