Cannot change my username back.

So I have been using the username "MutatedGrape" for a while, and my username currently is 3_14zza, I tried to change it back to MutatedGrape but when I tried it came up with "Username is already taken".

I was confused and started looking into it. I came up with that it thought I was using the word "Rape" inside my username. So right now, I cannot change my username back into my original name. I was thinking maybe you should look more into it? I really want to keep my original username, and this might be somewhat of a problem to other players as well in the future.