Also, if you have added a reference list on that session before attempting to add an existing reference,the "Save Page" button becomes enabled but if you go to the Review your changes section there is no entry for adding <references> there.

After clicking on "Save Page" , you will see the reference list did not get added in the page , but you open VE , you will the reference list

Change 130734 had a related patch set uploaded by Jforrester:
Make inserting existing references work again

https://gerrit.wikimedia.org/r/130734

Change 130734 merged by jenkins-bot:
Make inserting existing references work again

https://gerrit.wikimedia.org/r/130734

Verified the fix in Betalabs

Verified the fix on test2

Verified the fix on production