Repro steps of one of problematic behaviours:
  1. Launch CreatorCompanion from start menu of Windows
  2. Launch CreatorCompanion again. Then a window of secound instance appears.
  3. Do "new project" on second instance. The view changes to "Please Wait..." appearance.
  4. Wait a moment. Then Unity opens up. (Maybe creating a project is completed on Unity side.)
  5. Second instance stick on "Please Wait..." view.
  6. Kill the second instance (by Alt-F4 for instance)
  7. Launch CreatorCompanion again. you see the project list is not updated.
I think it should be prevented to launch multiple instances as Unity Hub does.