When your two popups (alerter itself, customization window) are up and you hit E two times (close window, open character screen), in some cases the customization window will stay open while the alerter window will be closed. In this case, if you left click the alerter again you will receive this message and a crash to main menu:

Error while running event on_tick (ID 0)
Error while running event Custom event (ID 87)
Gui element with name message-broadcaster.settings_container already present in the parent element.
stack traceback:
CircuitAlerter/actors/circuit-alerter-actor.lua:731: in function 'open_message_broadcaster_gui_for_player'
CircuitAlerter/actors/circuit-alerter-actor.lua:193: in function 'openGui'
CircuitAlerter/lib/actor_system.lua:76: in function 'openGui'
CircuitAlerter/control.lua:187: in function <CircuitAlerter/control.lua:186>
[C]: in function 'raise_event'
CircuitAlerter/lib/events.lua:20: in function 'opened'
CircuitAlerter/lib/events.lua:55: in function 'raiseEvents'
CircuitAlerter/control.lua:177: in function <CircuitAlerter/control.lua:172>
stack traceback:
CircuitAlerter/lib/events.lua:20: in function 'opened'
CircuitAlerter/lib/events.lua:55: in function 'raiseEvents'
CircuitAlerter/control.lua:177: in function <CircuitAlerter/control.lua:172>