You could duplicate the procedure mentioned here:
Designer logs are a little trickier; look in
~/.ignition/clientlauncher-data/designerlauncher.log. There will be a line starting with "Starting Java with the following parameters:". Copy the long command the comes after that, paste it into a new terminal, run it to launch a new Designer. All the logs will be dumped into the terminal as the Designer runs.
Then perform the action that kills the designer; if there's some exception being thrown it should be captured and logged in your running terminal.