CSL editor: Want 'et al use first' to work with all publications

Hi there, I'm having as issue with CSL editor. I need my in-text citations to be structured with an et al., if there are 3 or more authors. I have achieved this by editing the 'et al min' = 3 and 'et al use first' = 1. However, some of my publications have very similar authors and years and the papers that have the same first author and year, BUT different second and third authors, are not adhering to et al use first' = 1, and are instead showing the first 2 authors, even though there are more than 3 authors on the paper. Could you please let me know how to fix this. I presume that it is cited this way to show that the papers are different, but i'd rather just have an a, b after the citations to show that they are different. Thanks Megan