My in text citations with APA format sometimes use "et al" when expected (more than two authors), and sometimes not (i.e. MacKenzie, Nichols, Hines, Knutson, & Franklin, 2003).
The official rule with APA:
If there are three to five authors, list all authors the first time, then use et al. for subsequent citations.
If there are six or more authors, use et al. even with the first citation.
If there are only one or two authors, then always list the names (no et al. in this case).
In my experience, the CSL for APA does the citations correctly. Can you explain a bit more about your citations and why you think there is an error?