Missing import clause when adding custom component

While testing patch for DTL-6670, I encounter another issue.
Code base is SB 2.0 b20 + patch from http://sqe-rb.us.oracle.com/r/21436/

Steps to reproduce :
- clean user custom library
- start tool with assertions enabled
- import UnlockCustom.jar to Library
- DND Keypad from Library to Content panel
- DND just added Keypad from Content back to Library panel (this step does not fail due to applied patch)
- open a new document and DND second added Keypad_1 on Content or Hierarchy

The Keypad appears unresolved in Hierarchy and indeed, there is no import for the Keypad (see attached Keypad_1.fxml which is the generated FXML stored in the user Library).