citation-style-language/styles

Set the disambiguate-add-names to false, as it was incorrectly set to "true" before.

There's no documentation, but here's an example from a published article:
http://www.sciencedirect.com/science/article/pii/S0016703717302247

Schrader et al., 2016a
D. Schrader, J. Davidson, T. McCoy
Widespread evidence for high-temperature formation of pentlandite in chondrites
Geochim. Cosmochim. Acta, 189 (2016), pp. 359–376

Schrader et al., 2016b
Schrader D., Fu R. and Desch S. (2016b) Evaluating chondrule formation models and the protoplanetary disk background temperature with low-temperature, sub-silicate solidus chondrule cooling rates. In Lunar and Planetary Science Conference, p. 1180.

These are then cited as Schrader et al., 2016a etc. in the text.