Endnote outputting mixed citation styles in same document

I am having problems with Endnote outputting a mix of citation styles (or possibly a broken citation style!) in the same document, despite applying the Endnote Frontiers Science style (official, from the Endnote website) throughout. Eg

...feline herpesvirus 1 (Thiry et al.) and terrapene herpesvirus 1-associated pneumonia in Eastern box turtles (Sim et al., 2014)...

and when I look at the final reference list I see that both references look correct and the same eg

Thiry, E., Addie, D., Belak, S., Boucraut-Baralon, C., Egberink, H., Frymus, T., Gruffydd-Jones, T., Hartmann, K., Hosie, M.J., Lloret, A., Lutz, H., Marsilio, F., Pennisi, M.G., Radford, A.D., Truyen, U., and Horzinek, M.C. (2009). Feline herpesvirus infection. ABCD guidelines on prevention and management. J Feline Med Surg 11, 547-555.

Sim, R.R., Norton, T.M., Bronson, E., Allender, M.C., Stedman, N., Childress, A.L., and Wellehan, J.F., Jr. (2014). Identification of a novel herpesvirus in captive Eastern box turtles (Terrapene carolina carolina). Vet Microbiol.

So I am at bit of a loss as to why one reference looks correct (author, year) and the other does not (author).