I'm using biblatex v2.5 and the biblatex-apa style v5.7.
I have a couple citations with the same first author, including one with six co-authors in 2008. This is the only publication with that first author that was published in 2008, so it should just show up as Ranney, et al. (2008) - at least as I understand APA guidelines (section 6.12 / p. 175 in my 6th ed. copy).
biblatex is instead printing it as Ranney, Rinne, et al. (2008), which I assume is to avoid ambiguous author lists. But again, I think this should only happen when you have the same first author on two pubs in a given year. This happens with
The extra weird thing is that other citations with this first author work out fine. For example, I have two pubs (with the same author list) correctly typesetting as Ranney, et al. (2012a) (and 2012b). But there are other cites with the same problem as well (e.g., Ranney, Cheng, et al., 2001, or Munnich, Ranney, Nelson, et al. (2003)).
So, I'm happy to do some hunting and hacking, but I'm not really sure where to start. In other words, please provide a partial answer even if you don't figure this one out!
(I also actually like the way biblatex is doing it, as I realize it helps me find references more easily. But it's not APA 6e per my reading.)