Ambiguous citation not working correctly

I’m having the same problem

May you help me to fix my citations with same author and same year?

Dear friend

I’m having problems: It’s appearing wrong letters when I cited references from same author and same year!!

Corrected expected:

(Gottsberger and Silberbauer-Gottsberger 2006a; b),

 

But is appearing in this way: with letter K, instead of “b”: 

(Gottsberger and Silberbauer-Gottsberger 2006a; k).

 

Expected: (Paulino-Neto 2014a, b, c)

Appearing:  (Paulino-Neto 2014a, h, n)

Thanks