I'm a little confused as to what you mean by it shows Box1 info.. After you have logged in the 3rd account, that window displays information from another account?, so you have 3 windows, and 2 with the same account (characters) displaying? That would be rather odd.
Normally issues like that would log out the first account, which would mean you are logging in the same account twice.
If you actually mean that the same account details appear during the login process, but you can over type them and it logs in, and then the next time around slot 1 has slot 3 details, you fix that, and then slot 3 has slot 1 details, then this would mean that both slot 1 and slot 3 characters are pointing at the same copy of the virtual files. This normally happens because you Copy a character, update the character name, but not the virtual file names.
The final choice is that the game launcher is not closing down between characters. It needs to. Although if this was the issue, I'd expect the second character to have issues too.
Other than that, I'm not really sure how to interpret it further.
Perhaps you could provide a
copy of your config if it is not any of the above.