Same problem here even after X8.0.1 update!
This is ridiculous! I was already annoyed with Endnote after the iPad app kept making duplicates aof all my references. Now I have to buy X8 because I updated to macOS Sierra but all I get in return is a buggy useless program.
I dont want to change to Mendley, but if the attitude of Endnote does not change I will seriously have to consider.