I JUST got a brand new 3ds XL the other day, and immediately did a system transfer. The "coming from" system decided that after reaching stage 6/6 (over an hour into the transfer), it wanted to disconnect for literally no reason at all. The new system did nothing. After that, I formatted the old system, packaged it up, and sold it. Now I am trying to link my nintendo ID to my new 3ds and it says it's already linked. Apparently I was wrong to assume formatting the old system would clear the link data? Hoping something can be done on nintendo's end, otherwise I'm screwed out of all the pokemon that were in my pokemon bank.
(No, the old system is no longer available to me, I cannot get a hold of the person I sold it to and have them do anything about it. At this point, I need to ask that Nintendo intervene and fix the issue for me)
(If there is anything I can do anywhere online, that may work as well)