Unintended changing of citation style within the same document

Hello everybody, I have a little issue in using endnote and hope that you may have a solution for my problem. I’m using the APA 6th citation style from the beginning on, and wrote a 90 pages document. While correcting the document I recognized, that the citation style is not uniform, not even for the same reference. For example: Sometimes a citation is inserted as (MrX et al. 2015) and several pages later the same reference is inserted as (MrX, MrY & MrV 2015).
Is there anything I can do about it, since updating the bibliography did not work.
Thank you very much, kindes regards, Philipp

Are you using Endnote online or desktop?

I am not sure unless you have edited the citation parameters from the out of the box. For APA 6th that I just downloaded, I see this as the citation for 1st time and 2nd time cites. If anything, I might expect an earlier cite to be longer if less than 6 (and never 3 et al). I don’t think Ambiguous citation directions should result in this either, if it is the same citation. (But it seems weird that ambiguous citations have 3 of the 4 options selected – if it uses all three that is complicated!)