I use the APA style, but sometimes the initials of a few authors are included in the citation. What is wrong?
There is probably nothing wrong. The APA style requires that if there are multiple authors with the same surname, they should be separated from each other in the citations by adding initials so that the citations are unambiguous. Note that this applies to authorship, so it is perceived as different authorship if you have different co-authors.
If it concerns the same author(s) but initials nevertheless appear, it is a good idea to check that the author’s name is written equally in the different references. The smartest thing is often to copy the contents of the author field from one reference and paste it into the other.