Don't work with FieldCollection

This my scenario:

• Entityform type: FORM1
• In FORM1 i have a field collection field: FC1
• In FC1 i have a entityreferencefield with autocomplete widget: ER1

In my ER1 i select checkbox" Forbid duplicates".

So, when i visit page to create my entityform type(FORM1)

• I select entity in ER1 and click on field collection button "add more item",
• Select the same entity and click on field collection button "add more item" but error not appear.
• Click on SUBMIT button but error not appear and the form is submit.