I did multiple Dsiware downgrade and for what I've seen and did:
before:
Source (NNID1: exploit game (fieldrunner or other)) ----- Target (NNID2 (the one you use))
Exploit!!!!!!
After:
Source (no NNID) ----- Target (NNID1: exploit game & NNID2 (the one you use))
// On the target you can either connect with NNID1 or NNID2, but keep in mind that the exploit game is linked with NNID1
You have 2 solutions if you want to keep NNID2 (the one you use) on target:
- don't do another system transfert, but you'll "lose" NNID1 with the exploit game.
- Call Nintendo and ask to move NNID1 back to the Source 3ds.
Voila, hope it help.
ps: tell me if I've made a mistake somewhere, we learn from mistake.