It's been a little while since I've done a dfpm migrate, but the two things that come to mind are DFM host credentials and snapmirror settings on the controllers.
1st - Can you do a 'dfm host diag <filer_id>' from the DFM against each controller in each filer pair? Specifically, you'll want to make sure the filer login/password is successful as well as the ndmp login/password. Both need to be accurate for the DFM to talk to the controllers properly for vfiler datamotion to work.
2nd - Are there any existing snapmirror relationships between the two filers? I'd doublecheck the snapmirror.access option is setup properly since the first error occurred after trying to initialize the baseline snapmirror relationship.
Hope this helps. If anything else comes to mind I'll reply to the post.