Library recovery doesn’t solve the problem. I have done it couple of times and it doesn’t fix the problem
Contacted technical support. They are aware of the problem but they do not have solution.
Check also this post as someone suggested which if off automatic synchronisation with EndNote web
http://community.thomsonreuters.com/t5/EndNote-General/EndNote-8-crashes-on-Sierra-10-12-4/td-p/134347