Comment 16 for bug 978430

Try clicking more slowly. I just reproduced it by holding the button down on the return key for a second. I have gnome-terminal auto-starting in the session and it starts scrolling from all the enter presses right after activating it.

And yes, without sending SIGTERM Onboard doesn't get the chance to clean up and release pressed keys. The linked branch does that and in case anything gets stuck it sends a SIGKILL too for good measure. That was just a suggestion, but perhaps you can re-use some of the pieces.

Another option may be to make the greeter log in on key release instead of key press when hitting return. Onboard wouldn't have to release any keys that way. I felt that was a more invasive change, though, so I haven't suggested it.