In text citation issue with APA 6th

Hi, I am using endnotes APA 6th style and have some issues wit my in text citations.

For some authors, I will get “Name First letter of Surname, Year” and for some “Name, Year”.
I checked and there is no issues regarding authors with the same name for the first occurence.
Please advise how I could fix this issue, in order to have all in the same style for my in text citations.

Many thanks in advance

You say you have checked, but if there are any differences, (initials/full given names, periods, spaces) for the two citations, it will assume they are two different authors and disambiguate them.  The only way to be absolutely shure is to copy from one and replace the others.