First off, I missed 60% of some good offers because the GTS told me that it was already traded, even though it wasn't. Then, I got my Turtonator that I deposited, randomly fuse, with the Arcanine I tried to trade for a Oranguru.
Here's this glitch, but with different Pokémon.
Please read the bold sentence below, and look at the image.Will you take Goodra?
Goodra was the original Pokémon I deposited.
This glitch lasts until you exit, take back your Pokémon, perform the glitch again, or trade normaly.
Just hope i wouldn't be banned for discovering just how glitchy, the GTS is.
On the plus side however, It's very fast to have your Pokémon traded.