Designer unusable after going into component

Steps to reproduce:

• create Qt Quick 2 UI with Controls
• switch to Designer
• pull ComboBox into the preview
• right click on the combo box and trigger 'Go into Component'
• qml2puppet seems to crash but not respawning (which it does in other cases)

Current result:

• Designer cannot be used anymore

Note: qml file contains

import QtQuick.Controls.Private 1.0

after triggering the 'Go into Component' which is red underlined and its tooltip contains several error messages.
Deleting this line and switching back to Designer, clicking on the MenuItem of the combo box hangs forever...