I'm not sure what's the problem, but I feel as though the problem is on PokeTransporter's end,
since I was already to import them.
I guess the only way is for you to have a box of them, and see which one is allowed through.
@Jovie I just did a test.
Interesting enough, I managed to transfer 2: Both at lv 68, both untouched (one KOR and one ENG).
Oddly enough, the Lv 100s one didn't transfer (KOR and ENG). (levelled using PKHeX, if that matters)