two accounts on the same computer, twice the same

Hi, i think its a bug:
Today i loaded me and myself (my main and my alt)
as usual, launched 2 instance of the game (2 are allowed)

but as i was tired i used twice the same login, that was very weird i needed a few second to understand it was twice the same.

then i logged one out and used the right credentials, but i couldn't invite my alt or see it. had to restart the client.

I dont use proxy or any other third party software.

I also sometime encounter disconnect but only on one account.

hope this help