@regentaenzer I added "quit.im" Social network to # by typing just "quit.im" and pressing Add button.
Then I tried to add an account to that Social network not han having correct credentials: I got "401 Unathorized" error message, as expected.
Then I registered at quit.im and tried to add this new account: it was successfully added, no freezing or restarts.
So I couldn't reproduce the problem, unfortunately. https://loadaverage.org/attachment/3821325