Duplicate References appearing in Citations

I am using Endnote X9, with CWYW on Word for Mac.

I have a couple of references where there is only one reference by that author and that year in my reference list, but when I try to cite it, CWYW is creating duplicates ie (Author, Year a) etc- with duplicates listed in the bibliography. How can I get rid of these duplicates and have all of the citations refer to the one (only) reference?