So today, I bought the Victini tin which had 5 booster packs and a Victini card. I redeemed all 5 booster codes on TCGO I had at once and it came up saying "Redeeming codes please wait." It was doing this for about 5 minutes so I clicked off the page and I somehow had 3 booster credits, so I went to the redeem page again. This time I did all 6 that I had (Victini tin + 5 boosters), but 3 at a time instead of all at once. Despite redeeming 3 before, I managed to redeem all the same codes a second time.
Thanks to this glitch, I have 8 booster credits instead of 6 ^_^
Thanks to this glitch, I have 8 booster credits instead of 6 ^_^